Method of borate-based crystal growing and laser generator

FIELD: physics.

SUBSTANCE: invention refers to borate-based material production technology for crystal growing from caesium borate or caesium-lithium borate which can be used as optical devices for wavelength transformation, in particular, laser generator. Method of crystal growing from caesium borate or caesium-lithium borate includes water dissolution of water-soluble caesium compound and water-soluble boron compound to produce aqueous solution, water evaporation from aqueous solution with or without baking to produce material for crystal growing, and melting of produced material to grow crystals from caesium borate. To grow crystals from caesium-lithium borate water-soluble caesium, lithium and boron compounds are used as initial components of raw material for growing.

EFFECT: invention allows for crystals grown from borate with excellent uniformity and reliability, with small consumptions and for the short period of time; besides, use of this crystal as optical device for wavelength transformation makes it possible to produce very reliable laser generator (laser oscillator).

13 cl, 4 ex, 21 dwg

 

The technical FIELD

The present invention relates to a method of producing crystal-based borate and to the generator of the laser radiation. More specifically, the invention relates to a new method of obtaining a crystal-based borate, with which you can easily get the crystal on the basis of cesium borate, which can be used as an optical device for converting the wavelength used to translate wave Nd:YAG laser or Nd:YVO4laser third harmonic. Using this method can also be obtained crystal-based borate, cesium-lithium, which can be used as an optical device for converting the wavelength used to translate wave Nd:YAG laser or Nd:YVO4laser in the fourth harmonic with high quality. The method according to the present invention provides excellent uniformity and reliability of the crystal at a low price and short time of manufacture. The invention relates to a generator of laser radiation, in which the crystal is used as an optical device for converting the wavelength.

PRIOR art

Recently, laser applications have been expanded to ultraviolet lithography, laser micromachining, laser melting, etc. and for these applications n the necessary generators of laser radiation, called in the materials of the present application as "laser oscillators", effectively generating stable to ultraviolet radiation. As one of the options for satisfying this need, has attracted great attention to the solid-state laser oscillator in which to convert the wavelengths of the light sources in the ultraviolet radiation used nonlinear optical crystals. For more efficient acquisition of ultraviolet radiation is necessary in order nonlinear optical crystals have high output power and high resistance to damage by laser radiation.

As nonlinear optical crystal for converting the wavelength into ultraviolet radiation have been used, for example, the crystals on the basis of lithium borate (LBO) crystals: LiB3O5), which have been adapted for practical use when converting radiation of the Nd:YAG laser or Nd:YVO4laser with a wavelength of 1064 nm in the third harmonic with a wavelength of 355 nm. However, for LBO crystals characterized by poor stability of the surface damage and low conversion efficiency of the wavelength, so there is a great need for new alternative nonlinear optical crystals, which would not be so easily damaged and both regional and high conversion efficiency of the wavelength. The inventors and other researchers have conducted extensive studies and as a result came to the conclusion that, as a nonlinear optical crystals, alternative LBO-crystals, can be considered the crystals on the basis of cesium borate (NWO-crystals: CsB3About5). ITS crystals have a constant optical nonlinearities in 2 or more times greater than the LBO crystals, and they can efficiently generate the third harmonic radiation of a Nd:YAG laser or Nd:YVO4-laser. So they can find practical application as a highly efficient nonlinear optical crystals converters wavelength. Additionally, proposed by the authors of the invention the crystals on the basis of cesium borate-lithium (CLBO) crystals: CsLiB8O10) can generate radiation with a shorter wavelength, for example - the fourth harmonic radiation of a Nd:YAG laser with a wavelength of 266 nm, converting the radiation with high conversion efficiency and a wide range of temperatures and tolerances on angles of incidence. The authors of the present invention have high hopes for these new, high converting a wavelength of nonlinear optical crystals (see reference [1]).

Usually crystals based on borates, such as ITS crystals and CLBO crystals, obtained as single crystals by heating and melting poroshkoobraznogo carbonate (raw material) and growing crystals of the obtained material for growing crystals using different methods of growing crystals. For example, in the case of ITS crystals authors of the invention directly mixed and melted by heating to 26.6 mol.% Cs2CO3and 73.3 mol.% In2About3and then grew crystals CsB3About5using the kyropoulos technique (Kyropoulos). However, this method has disadvantages that it is difficult to homogenize the composition of the melt, added inclusion during crystal growth are distributed in the whole volume of the crystal, which leads to strong scattering and poor resistance to damage by laser radiation (see reference [2]).

So next, the inventors mixed 30 mol.% Cs2CO3and 70 mol.% In2About3that melted mixture by heating and grown crystals CsB3O5using a combination of TSSG-machinery and equipment mixing the solution, which consists in placing in solution propeller stirrer and the rotation of the crucible. Although this method can significantly reduce the scattering in the grown crystal, the liquid rapidly evaporates from the surface of the liquid, so that it is difficult to achieve crystal growth, and crystal cannot be grown in a long time (see reference [3]).

In all the above ways the original powdered materials directly mixed and used as source material for growing crystals, when et is m powders emit gas bubbles due to decarboxylation during thermal melting and swelling during the reaction. To prevent this, the powders are mixed and melted gradually, in several separate operations. Therefore, upon receipt of ITS crystals and CLBO crystals original powder material is melted by heating in a furnace for several days, and then cooled to a standard temperature, the resulting material for growing crystals is transferred to a furnace for growing crystals and melt, melt grown single crystals. Accordingly, the standard way to get FREE crystals and CLBO crystals has drawbacks consisting in large time-consuming and expensive.

The present invention was created after analysis of the above information. The present invention is to overcome these common problems and providing a new way to easily obtain, at low cost and in a short period of time, high-quality crystals based on borates with excellent uniformity, which can be used as an optical device for converting the wavelength and the like, and a laser oscillator in which these crystals would be used as an optical device for converting the wavelength.

Reference [1]: Y. Mori et al., "New nonlinear optical crystal: Cesium lithium borate (New nonlinear optical crystal: Borat is Asia-lithium"), Appl. Phys. Lett., 67, 13 (1995) of 1818.

Reference [2]: Y. Kagebeyashi, Y. Mori and T. Sasaki, "Crystal growth of cesium triborate, CsB3O5by Kyropulos technique" ("Growing crystals triborate cs, CsB3About5using techniques kyropoulos"), Bulletin of Materials Science, Vol.22 (6), pp.971-973, 1999.

Reference [3]: H. Kitano "Efficient 355-nm generation in CsB3About5crystal" ("Efficient generation of radiation with a wavelength of 355 nm in CsB3O5crystal), Optics Letter, Vol.28, No.4, pp.263-265, 2003.

The INVENTION

To solve the above problems according to the first aspect of the invention provides a method of obtaining a crystal-based borate, which comprises dissolving a water-soluble compounds of cesium and water-soluble boron compounds in water to obtain an aqueous solution, the evaporation of water from the aqueous solution with subsequent sintering or without sintering to obtain a starting material for crystal growth and melting the resulting material for growing the crystal on the basis of cesium borate.

According to the second aspect of the invention provides a method of obtaining a crystal-based borate, and a water-soluble compound of at least one of alkali metals and alkaline earth metals, different from cesium, is dissolved in water together with the connection of cesium and boron compound for growing crystal on the basis of cesium borate b is Otto-formula

Cs1-xMxB3O5(0≤x<1),

where M is an alkali metal or alkaline earth metal.

In addition, according to the third aspect of the invention provides a method of obtaining a crystal-based borate according to the first aspect of the invention, and as source material for growing a crystal on the basis of cesium borate-lithium use of water-soluble compounds of cesium, lithium and boron. According to a fourth aspect of the invention, a method of obtaining a crystal-based borate, and a water-soluble compound of at least one alkali metal or alkaline earth metal, different from cesium or lithium, dissolved in water together with a compound of cesium, lithium compound and a boron compound for growing crystal on the basis of cesium borate-lithium with gross-formula

Cs1-xLi1-yMx+yIn6About10(x=0; y<1) or

Cs2(1-z)Li2M2In12About20(0<z<1),

where M is an alkaline metal or alkaline earth metal. Additionally, according to the sixth aspect of the invention provides a method of obtaining a crystal-based borate according to any one of the above aspects, wherein the water-soluble compounds of cesium carbonate is a connection. According to the seventh aspect provides a method, wherein vodorastvorimym the boron compound is boron oxide or boric acid. According to the eighth aspect provides a method, wherein the aqueous solution is heated to evaporate water. According to the ninth aspect provides a method, wherein after the evaporation of water from aqueous solution conduct sintering, which is carried out in the temperature range from 500°and above, but below the melting temperature. According to the tenth aspect provides a method, wherein the molten material for growing mixed crystals during growth of the crystal. According to the eleventh aspect provides a method, characterized in that the growing crystal is heated to reduce the degree of contamination of the crystal water. According to the twelfth aspect provides a method, characterized in that the grown crystal is heated to a temperature of 100°C or higher. According to the thirteenth aspect provides a method, characterized in that the grown crystal is heated in gossamery atmosphere or under vacuum.

In addition, according to the fourteenth aspect of the invention provides a laser oscillator (laser radiation)containing a crystal-based borate obtained by the method according to any of the above aspects, as an optical device for converting the wavelength.

A BRIEF DESCRIPTION of GRAPHIC MATERIALS

Figure 1 is the tsya a schematic depiction, illustrating the stage of obtaining sintered bases crystal-based borate according to the method of the present invention.

Figure 2 is an image illustrating an example implementation of the invention using a cylindrical resistive heating furnace for growing a crystal on the basis of borate according to the present invention.

Figure 3 is a side view, illustrating details of the growing crystal on the basis of borate according to the present invention.

Figure 4 is a graph illustrating the measurement results of x-ray diffraction: (a) the standard material for crystal growth, (b) on material for growing crystals according to the present invention) on ITS single-crystal.

Figure 5 is an image based on a photograph showing the crystal on the basis of cesium borate obtained according to the method of the present invention.

6 is a structural diagram illustrating an apparatus for generating a third harmonic radiation with a wavelength of 1064 nm using a crystal on the basis of cesium borate obtained according to the method of the present invention.

7 is a graph illustrating the output power of the ultraviolet radiation of the crystal based on the cesium borate obtained according to the method of this image is to be placed.

Fig is an image illustrating the results of differential thermal analysis standard materials for growing CLBO crystals, mixed in a mortar.

Figure 9 is an image illustrating the results of measurement of x-ray diffraction on a powder sample, a corresponding Pig, after differential thermal analysis.

Figure 10 is an image illustrating the diffraction peaks of x-ray radiation for CLBO crystal.

11 is an image illustrating the results of differential thermal analysis of the material for growing crystals obtained according to the method of the present invention.

Fig is an image illustrating the results of measurement of x-ray diffraction on powder samples, corresponding to 11, after differential thermal analysis.

Fig is a schematic depiction illustrating the structure of the optical system for measurement of the threshold of damage of ultraviolet laser radiation.

Fig is an image illustrating the results of measuring thresholds of damage by laser radiation for (a) fused quartz, (b) standard crystal, the crystal obtained according to the method of the present invention.

Fig is an image, illustrious exemplary embodiment of the invention with stirring the solution for crystal growth.

Fig is an image illustrating the results of measurement of properties of the sample, mixed as directed on Fig.

Fig is an image illustrating the results of evaluation of the content of Oh-groups in CLBO-the crystal method, infrared adsorption spectroscopy with Fourier transform (FT-IR).

Fig is a schematic depiction illustrating the structure of the optical system for measuring threshold internal damage of ultraviolet laser radiation.

Fig is an image illustrating the results of measurement of threshold internal damage by laser radiation for CLBO crystal heated to 150°s, when irradiation of multiple pulses.

Fig is an image illustrating the results of measuring the content of Oh-groups in CLBO-crystal heated to 150°With, by way of infrared adsorption spectroscopy with Fourier transformation.

Fig is an image illustrating the results of measurement of threshold internal damage by laser radiation for CLBO crystal heated to 150°C.

Digital signs in the figures represent the following:

1. Polymethylpentene tank

2. Ion-exchange water

3. The crucible

4. Heater

5. Cylindrical resistive heating furnace

6. A small hole

7. Bare to istall

8. The support rod to the seed crystal

9. Molten substance

10. Nd:YVO4laser

11. Non-linear optical crystal

INFORMATION CONFIRMING the POSSIBILITY of carrying out the INVENTION

The present invention is characterized by the above-described aspects and embodiments of the invention described below.

A method of obtaining a crystal-based borate according to the present invention is characterized by the fact that it includes a stage of dissolution of water-soluble starting materials in water to obtain an aqueous solution, evaporating water from the aqueous solution with subsequent sintering or evaporation of water without sintering with obtaining material for growing the crystal, the melting point of the obtained material for growing crystal and the growing crystal.

This method is based on the new data obtained in the studies performed by the inventors. These new data are that upon receipt of the crystals based on borates, such as crystals on the basis of cesium borate (NWO-crystals or crystals on the basis of cesium borate and lithium (CLBO crystals), an important factor in determining the quality of the crystals is uniform mixing of the starting compounds in obtaining materials for growing crystals. Even in the case of use as the original Mat is Rial carbonate compounds important to translate carbonic acid in easily removable state, ensuring, thus, the ease of uniform mixing.

Accordingly, the inventors paid attention to the solubility of cesium and lithium, which, together with boron, are the main elements crystals based on borates. The inventors have discovered that an aqueous solution of a homogeneous composition can be obtained by mixing a water-soluble starting materials, i.e. compounds of cesium, lithium compounds and the boron compounds in pre-determined proportions and adding water to obtain an aqueous solution in which the raw materials are uniformly mixed in water at the molecular level. The aqueous solution is subjected to evaporation and solidification, if necessary bake, obtaining material for growing crystals, and the resulting material is melted and grown crystal. Thus it is possible to get crystal clear on the basis of borate with a small number of scattering the light.

More specifically, for example, in the case of obtaining FREE crystal, water dissolve water-soluble compound of caesium and water-soluble boron compound to obtain an aqueous solution. In the case of receiving a CLBO crystal in water is dissolved a water-soluble compound of cesium, lithium compound and a boron compound to obtain an aqueous solution. The water from the aqueous solution is evaporated, and R is sulfiruyuschie substance is sintered or use, as it is, to obtain material for growing the crystal, which is melted and grown crystal.

In addition, in the method according to the present invention in water can be dissolved with a water-soluble compound of at least one of alkali metals and alkaline earth metals, different from cesium or lithium. More specifically, for example, upon receipt of the crystal-based borate, cesium, cesium (Cs) in the CsB3About5you can replace the alkali metal that is different from cesium, for example sodium (Na), potassium (K) or rubidium (Rb), or alkaline earth metal such as barium (BA), strontium (Sr), calcium (CA) or magnesium (Mg), to obtain the crystal having the molecular formula

Cs1-xMxIn3O5(0≤x<1),

where M is an alkaline metal or alkaline earth metal.

Upon receipt of the crystals on the basis of cesium borate-lithium part cesium and lithium in the composition CsLiB6About10you can replace any alkaline metal or alkaline earth metal of the above with obtaining a crystal having the formula

Cs1-xLi1-yMx+yIn6About10(x=0, y<1)

Cs2(1-z)Li2M2zBi2O20(0≤z<1),

where M is an alkaline metal or alkaline earth metal.

For example, the composition corresponding to 0<x<0,01 that saloon the second metal (M) is Na (sodium), compositions corresponding to 0<x≤0,1, where M is K (potassium), and compositions corresponding to 0<x≤1, where M is Rb (rubidium), preferable from the point of view of the process of obtaining, physical properties, etc. of the Composition, of course, can contain any alkali metals and alkaline earth metals, if they are in the specified range.

Accordingly, alkali metal or alkaline earth metal, different from cesium or cesium and lithium is present in the crystal structure in the form of ion, whereby the refractive index of the resulting crystal may change with improved angle negotiation phase, angle tolerance, temperature tolerance, etc. and can also change the crystal structure, resulting in possible to obtain more stable crystal, in which it is difficult to get the crack, which is not cloudy, etc.

As is clear from the above description, the crystals on the basis of cesium borate used in the present invention include oxide crystal, consisting only of and cesium borate and having a molecular formula of CsB3O5and crystals, having a molecular formula of Cs1-xMxIn3O5in which part of caesium in CsB3O5replaced by alkali metal or alkaline earth metal (M)in contrast to cesium. The crystals on the basis of Borat caselite, used in the present invention include oxide crystal, consisting only of cesium, lithium borate and having a molecular formula of CsLiB6About10and crystals, having a molecular formula of Cs1-xLi1-yMx+yBe6O10and Cs2(1-z)Li2M2zB12O20in which part of the cesium and lithium CsLiB6O10replaced by another alkali metal or alkaline earth metal (M).

According to the present invention, the source materials are dissolved in water to obtain a homogeneous aqueous solution and, having thus grinding and uniformity, use them to get material for crystal growth. Examples of water-soluble compounds of cesium, lithium and other alkali and alkaline earth metals, used as starting materials in this invention are salts of inorganic acids, such as carbonates, and organic acid salts such as acetates. In particular, if the starting material used is a water-soluble carbonate or cesium lithium and dissolve them in water, carbonic acid can be easily removed, and therefore it is possible to reduce the number of bubbles caused by decarboxylation at the stage of firing or dissolution. Preferred boron compounds include water-soluble boron oxide and boric acid, which is easily soluble in water, since the use of these compounds raw materials it is easy to evenly mix, although it is possible to use other water-soluble boron compounds.

The raw materials preferably should be in a powdered form that promotes their dissolution in water, even though the state of source materials in the present invention are not specifically limited. Preferably, the raw materials, such as cesium carbonate, lithium carbonate, and boron oxide (or boric acid) was mixed with water at the same time. As a result of research conducted by the inventors, it was confirmed that the method with simultaneous mixing raw materials such as water is more preferable than the method of mixing the aqueous solutions prepared separately by dissolving each of the materials in the water. The amount of water for dissolving the source materials should preferably 1.0 to 2.5 times the total weight of raw materials upon receipt of the crystal-based borate, cesium and should preferably 1.2 to 2.5 times the total weight of raw materials upon receipt of the crystal-based borate, cesium-lithium. In both cases, more preferably, the amount of water in 1.5-2 times the total weight of starting materials. If the amount of water is less than B1,0-1,2 times the total weight of starting materials, requires more effort to complete dissolution of the starting materials. It should be noted that if the source materials do not dissolve in water, the solubility can be improved by heating the aqueous solution. On the other hand, if the amount of water is more than 2.5 times the total weight of starting materials, the aqueous solution can be prepared easily, but requires a lot of time the next stage of evaporation of water.

The ratio between the starting materials depends on the type of these materials, the amount of water, etc. In the case of carbonate, cesium (Cs2CO3with boron oxide (2About3) or boric acid (H3IN3) to get the crystal on the basis of cesium borate, a molar ratio of Cs:B is preferably 1:2,13-4,56. In the case of carbonate, cesium (Cs2CO3), lithium carbonate (Li2CO3) and boron oxide (2O3) or boric acid (H3IN3to obtain crystal-based borate, cesium and lithium, the molar ratio of Cs:Li:B preferably is 1:1:3-10. In other cases, these relationships can be used as a standard.

According to the present invention after preparation of the aqueous solution of the water is evaporated. Water can evaporate naturally, but if you heat the aqueous solution, this is what contributes to the complete dissolution and mixing of materials. Accordingly, in contrast to mechanical pulverization and mixing using a ball mill and the like, the materials can be mixed and uniformityof to the microscopic level using procedures in accordance with the present invention. Furthermore, the method according to the present invention does not create a risk of non-uniformity composition due to contamination by impurities.

Through the evaporation of water from evenly mixed aqueous solution in which the raw materials are uniformly mixed at the molecular level, get a solid substance. According to the present invention, the solid can either bake or use as is, to obtain material for crystal growth. The sintering is preferably performed at a temperature equal to 500°s or higher and lower than the melting point, and the most practical to the sintering temperature was equal to 500-700°C. the sintering Time may be equal to about 10 minutes and several hours of sintering is enough, even if complete removal of hydrates, although the sintering time depends on the number and degree of dryness of the material, etc. In the case of use as the source of carbonate material in the sintering step and there are almost no swelling of the material due to decarboxylation. Accordingly, in the ü can be directly placed large quantities of materials, due to which the production time can be greatly reduced, to about 1/5 of the time required when using standard methods, and due to this can be ensured by reducing costs. In addition, since the raw materials are uniformly mixed at the molecular level can be obtained FREE crystals and CLBO crystals with excellent crystallinity. Also when growing for long periods of time can be obtained in large crystals.

More specifically, for example, when a water-soluble compound of cesium in the form of carbonate (Cs2CO3) and water-soluble boron compound in the form of boron oxide (2About3) is dissolved in water to obtain a crystal-based borate, cesium, according to the present invention, the decarboxylation reaction represented by the following equations is carried out by neutralization.

In2O3+H2O→NO2

CsCO3+NO2→2CsBO2+H2O+CO2

In the case of a crystal-based borate, cesium-lithium according to the method of the present invention to add water-soluble lithium compound in the form of carbonate (Li2CO3this is in addition to the reactions described above formulas, is the decarboxylation reaction, describing the may by the following equation:

Li2CO3+NO2→2LiBO2+H2O+CO2

The standard method of getting FREE of crystals and CLBO crystals such decarboxylation reaction occurs at the stage of sintering, when the melt viscosity is quite high, so that the melt greatly increases in volume. However, according to the present invention decarboxylation reaction occurs in aqueous solution, therefore, swelling of the source materials is not happening, and for once it is possible to process large quantities of materials. After neutralization of the water is evaporated by natural means or by heat curing the mixture thus formed CsBO2and LiBO2evenly mixed on a microscopic level. Then again produce sintering, while having crystal CsB3O5according to the reaction:

CsBO2+2O3→CsB3O5

upon receiving HIS crystal, or the crystal CsLiB6O10through reaction:

CsBO2+LiBO2+2V2About3→CsLiB6O10

when receiving a CLBO crystal, the crystals are uniform and homogeneous at the microscopic level.

However, the sintering is no need to perform, and whether you are sintering or not, the resulting material for growing crystals PLA is it for growing crystals according to the present invention. The growing crystal can be carried out by heating to the melting point or higher and then use one of the various methods of growing crystals.

Thus obtained melt has a crystallinity, a high degree similar to the crystallinity of the single crystal, and therefore it can otvetit as it is and use in various applications. Alternatively, the melt can be used for growing a single crystal by known methods of growing crystals. In this case, can be grown high quality single crystal.

According to the present invention it is not necessary to prepare the melt in the melting furnace as in standard ways. Accordingly, it is possible to prepare the melt in the furnace for crystal growth and consistently grow crystals.

By mixing the molten material for growing crystals in the process of growing crystals that melt can be even more uniformitarian, so can be obtained beneficial effects, including increased tolerance to damage by laser radiation and the reduction of variation of the threshold of resistance to damage by laser radiation. For example, the phase mixing of the melt can be carried out through the ω rotation of the seed crystal around the axis of the support rod to the seed crystal and the rotation of the crucible in the direction opposite to the direction of rotation of the seed crystal with a periodic change of the direction of their rotation or by placing in the melt paddle agitator and rotating together with the crucible, etc.

According to the method of obtaining a crystal-based borate of the present invention is a growing crystal can be heated, as described above, to reduce water impurities in the crystal. In the course of research conducted by the inventors, it became clear that not only the crystals based on borates, obtained according to the present invention, but the standard crystals based on borates contain water contamination, and not adsorbing on the surface and inside of the crystal. As a result of further intensive studies, the inventors have found that by reducing the impurity content of the water in the crystal can increase the threshold level of damage to the crystal by the radiation of ultraviolet laser. The above-described stage of heating based on this radical new discovery. The threshold level of damage by laser radiation increases with decreasing water impurities in the crystal. For example, if the crystal-based borate grown according to the present invention, simply heat up the heater to a temperature equal to 100°With or higher, for example up to 150°the content of water pollution on tapeno reduced and the threshold level of damage by laser radiation gradually increases, this increase becomes insignificant after about 100 hours. The threshold level of damage to the UV laser can be increased approximately 1.35 times by heating to 150°C for 100 hours or longer. Stage heating can be performed using various heating devices instead of heaters and heating devices can be used in the atmosphere with the substitution of gas or vacuum.

According to the method of producing crystals according to the present invention, the crystal-based borate can be obtained easily at low cost in a short period of time. In addition, the raw materials can be uniformly mixed at the molecular level, and the resulting crystal will have transparency, high quality with homogeneous composition, a significantly smaller scattering and high resistance to damage by laser radiation. For example, if the crystal on the basis of cesium borate obtained according to the method of the present invention, use of a laser oscillator as the nonlinear optical crystal for converting the wavelength (optical device for converting the wavelength), then the crystal will not be damaged by laser radiation at the stage of generation of mA is masnago ultraviolet radiation, unlike standard crystals on the basis of cesium borate. As specified crystal will give the output power is much greater than that of the crystals on the basis of lithium borate, so it can be used in the device for generating a third harmonic Nd:YAG laser or Nd:YVO4laser, etc. If the crystal-based borate, cesium-lithium obtained according to the method of the present invention, use of a laser oscillator as the nonlinear optical crystal for converting the wavelength, the crystal will be less damaged by laser radiation at the stage of generation of low-power ultraviolet radiation than fused silica and standard crystals based on cesium borate-lithium, and the band allocation threshold is stable, so it can be used as a device for generating fourth harmonics and as a device for the generation of the third harmonic. Accordingly, when using a crystal-based borate obtained according to the method of the present invention, as an optical device for converting the wavelength of ultraviolet radiation can be obtained stably and efficiently, and can be provided more reliable laser oscillator (laser radiation). This is extremely important for building high performance is ultrafioletoviy laser system using crystal-based borate.

The embodiments of the present invention will be more fully explained below in connection with examples and the accompanying drawings. The invention is not limited to the following examples, and it will be obvious that there may be various changes in details.

DESCRIPTION of embodiments of the INVENTION

Example 1

Crystal-based cesium borate was obtained according to the example of the method of obtaining crystals based on borates according to the present invention.

First, as shown in figure 1(a)-1(d), ion-exchange water (2) was placed in polymethylpentene tank (1)having a diameter of 20 cm and a height of 26 cm, and heated to about 100°in the melting furnace, (2) was added to a homogeneous mixture 4337,4 g Cs2CO3and 2162,6 g2About3the mixture is melted and evaporated the water by prolonged heating. Then, after water evaporation, the remaining material was placed in an open platinum crucible (3)having a diameter of 15 cm and height 15 cm, dried and utverdili by heating up to 300°and probalily at 650°With obtaining material for growing the crystal. The crucible (3) was placed in a cylindrical resistive furnace for crystal growth with a five-level adjustment (5)having heating elements (4), as shown in figure 2, and the upper hole of the cylindrical resistive furnace (5) C the wing insulating material, had a small hole (6) for transferring the seed crystal on the area corresponding to the center of the crucible (3).

Then, the inner temperature in the furnace was increased to 850°for melting material for growing crystals, this temperature was maintained for 1 hour, the melt was placed stirrer consisting of aluminum rod with platinum blade, fixed at its lower end, and stirred melt within 24 hours. Then, the inner temperature of the furnace was lowered to 787,5°and, as shown in Figure 3, recorded the seed crystal CsB3About5(7), cut along the a-axis at the lower end of the seed crystal holder (8) using a platinum wire, coined the seed crystal (7) in the crucible (3) through a small hole (6)provided in the upper part of the cylindrical resistive furnace (5), shown in figure 2, and brought into contact with the liquid surface of the melt (9). The holder of the seed crystal (8) is rotated during slow cooling speed of 0.1°/day for growing crystal from the seed crystal (7). The rotation speed was 60 rpm, and the rotation direction is reversed after every 3 minutes.

After 10 days, when the crystal growth was completed, the crystal was separated from the liquid melt (9) and slowly cooled to room temperature, PR is the cooling rate, equal to 20°C/hour, to obtain a transparent single crystal CsB3About5size 10 mm×19 mm×19 mm

Example 2

Crystal-based cesium borate obtained according to the method of the present invention under conditions different from the conditions of example 1, this crystal-based cesium borate was used as the nonlinear optical crystal and evaluated its properties.

As shown in figure 1, the ion-exchange water (2) was placed in polymethylpentene tank (1)having a diameter of 20 cm and a height of 26 cm, and heated to about 100°in the melting furnace, (2) was added to a homogeneous mixture 4671,1 g Cs2CO3and 2328,9 g2About3the mixture was dissolved and continuing heated, steamed water.

After evaporation of the water remaining material was placed in an open platinum crucible (3)having a diameter of 15 cm and height 15 cm, dried and utverdili by heating up to 300°and probalily at 650°C. In the measurement result of x-ray diffraction on the received material for growing the crystal were obtained peaks, characteristic for ITS crystal, as shown in Figure 4(b). Figure 4(a) shows the measurement results of x-ray diffraction on the test material for growing crystals obtained by the standard method in which the powdery raw materials directly from Asali and spec. Figure 4(a) there are many peaks that differ from the highs of HIS crystal. Figure 4(C) shows the measurement results of x-ray diffraction on the ideal FREE crystal.

Then the crucible (3) was placed in a cylindrical resistive furnace for crystal growth (5)having heating elements (4), as shown in figure 2, and the upper hole of the cylindrical resistive furnace (5) closed insulating material having a small hole (6) for transferring the seed crystal on the area corresponding to the center of the crucible (3).

Then, the inner temperature in the furnace was increased to 850°for melting material for growing crystals, this temperature was maintained for 3 hours, the melt was placed stirrer consisting of aluminum rod with platinum blade, fixed at its lower end, and stirred melt within 12 hours. Then, the inner temperature of the furnace was lowered to 788°and, as shown in Figure 3, recorded the seed crystal CsB3About5(7), cut along the a-axis at the lower end of the seed crystal holder (8) using a platinum wire, coined the seed crystal (7) in the crucible (3) through a small hole (6)provided in the upper part of the cylindrical resistive furnace (5), shown in figure 2, and brought into contact with the surface of the liquid melt (9). The holder of the seed crystal (8) is rotated during slow cooling speed of 0.1°/day for growing crystal from the seed crystal (7). The rotation speed was 60 rpm, and the rotation direction is reversed after every 3 minutes.

After 16 days, when the crystal growth was completed, the crystal was separated from the liquid melt and slowly cooled to room temperature at a cooling rate equal to 16°C/hour, to obtain a transparent single crystal CsB3O5size 25 mm×30 mm×30 mm Figure 5 is a photograph showing an example of NWO-crystal obtained according to the present invention, and clearly showing that HIS crystal obtained by the method according to the present invention, had been transparent.

This single crystal was used as the nonlinear optical crystal. As shown in Fig.6, 4 types of nonlinear optical crystals (11), including THEIR crystal obtained by mixing starting materials in an aqueous solution FREE crystal obtained by mixing the solution, ITS crystal obtained in the standard way, and LBO-crystal were used for frequency conversion of laser radiation having a wavelength of 1064 nm and a repetition frequency of 31.25 kHz, generated by the source of the manhole the aqueous radiation Nd:YVO 4laser (10) (LIGHTBOOK 2010). Generated thus the third harmonic of the split prism, and the output power was measured with a power meter.

The results are shown in graph 7. As shown in Fig.7 FREE crystal obtained by mixing starting materials in an aqueous solution according to the present invention, although showed a lower output power of the ultraviolet radiation with a wavelength of 355 nm than SVO-crystal obtained by mixing the solution, it has a damage threshold of the laser radiation, equal to 110 MW/cm2or more, higher than the damage threshold of the laser radiation standard FREE crystal, which is equal to 60 MW/cm2or more, and the damage threshold of the laser radiation LBO crystal, which is equal to 80 MW/cm2or more. These data indicate that the WWTP-crystal according to the present invention is less damaged by laser radiation than the standard SVO-crystal. In addition, NWO-crystal according to the present invention had a maximum output power equal to 2.9 W and the efficiency of conversion 1.44 times higher than the efficiency of conversion of the LBO crystal, which shows that it is of high quality.

Example 3

In the standard process of growing CLBO crystal, as used by a large number (6 to the) raw materials and the increase in volume due to decarboxylation under heating, powdered Cs2CO3, Li2CO3and In2About3loaded into a platinum crucible without mixing and firing, and then heated to 900°and melt with obtaining the solution for crystal growth. In this case, there is a probability that in the heating process In2About3having the lowest melting temperature of the source material will melt first, and Cs2CO3andLi23will PLASTICA in In2O3. Therefore, it is expected that during melting unevenly mixed raw materials of high viscosity of the original material on the basis of boric acid will be bad to diffuse, the result of which will form the local areas with a high content of Cs and Li, and it will be difficult to get the composition and structure of the CLBO needed for growing crystals.

Therefore, the inventors have tried to obtain a CLBO crystal phase by firing the starting material. The original stoichiometric materials were weighed, mixed in a mortar and subjected to differential thermal analysis (DTA). The heating rate was 10°C/min, and the temperature was raised to 700°C. approximately at 430°and at 540°observed endothermic reaction, as shown in Fig. Endothermic reaction at a temperature of about 430°With, apparently is, is melting In2About3but the reaction at a temperature of about 540°Since, apparently, is a synthesis of CsLiB6O10(CLBO).

After DTA raw materials were subjected to measurement of x-ray diffraction on the powder, and the obtained results, shown in Fig.9. Figure 9 is seen not only diffraction peaks CLBO, but the highs for contaminants such as CsB3About5and Li2B4O7; diffraction peaks CLBO shown in Figure 10. It is believed that the process of mixing in a mortar provides only limited miniaturization and uniformization, and in the raw materials are formed a local inhomogeneity of the composition so formed pollution. Accordingly, people have been searching for way miniaturization and uniformization raw materials.

Crystal CLBO easily absorbs moisture, components and raw materials are hygroscopic, so it was thought that the source materials, it is desirable to weigh and mix at low humidity. The inventors have analyzed these properties from a different angle of view and dissolved materials in the water to use the hygroscopicity in the method according to the present invention for achieving the small and uniform mixing. When placing 100 g of the starting materials, weighed stoichiometric, about 500 ml vodyane dissolved with the formation of bubbles. After separation bubbles formed aqueous solution was colorless and transparent, which showed that the starting material was completely dissolved. After dissolution in water2O3converted into boric acid, and Cs2CO3and Li2CO3find alkaline properties. Therefore, apparently, there is a neutralization reaction. The bubbles in this reaction are formed by the decarboxylation Cs2CO3and Li2CO2and, apparently, the compounds of carbonic acid contained in the original materials, completely disappear, because the number of In2O3enough to convert compounds of carbonic acid into compounds of boric acid. After evaporation and drying an aqueous solution was obtained a white powder.

The powder was subjected to DTA in the same manner as described above. In the observed exothermic reaction at about 540°S, as shown in figure 11.

The powder after DTA was subjected to measurement of x-ray diffraction on the powder, and as a result were only detected maxima CLBO without highs of these contaminants, as shown in Fig. Therefore, it was concluded that the original materials miniaturization and uniformitarian by mixing in aqueous solution. In the case of face (211), with 2θ=21,38°where was the greatest di is raccoony maximum CLBO-phase, was received with the greatest intensity maximum of about 16,000 CPS, whereas the sintered body obtained from raw materials, processed in the standard way, given the intensity equal to 1500 pulses/sec. This is likely due to the fact that the fusion reaction according to the following equation accelerated by decarboxylation.

CsBO2+LiBO2+2V2About3→ CsLiB6O10

On the basis of these results, the material for the crystal growth was obtained in the following way. As starting materials there were used commercially available Cs2CO3with a purity of 4N, Li2CO3with a purity of 3N and a2O3. For growing crystal TSSG-way was prepared 6 kg of source material in the form of a self-fluxing composition with a molar ratio of Cs2COC:Li2CO3:In2CO3=1:1:5,5, i.e. the number of In2O3was slightly reduced. The weighed raw materials were dissolved in about 6 liters of distilled water, was subjected to evaporation and dried, and the obtained powder was subjected to calcination at 800°C for 24 hours. In this case, because the decarboxylation occurred at the stage of dissolution in water, no swelling, as in the case of standard cooked raw materials. Part of the obtained material for virusiv the deposits of crystals (sintered body) was subjected to measurement of x-ray diffraction on the powder, and the result of this measurement showed the presence of only CLBO-phase. Then the material was heated to 900°With a melt.

The crystal is grown conducted using cylindrical resistive furnace with five-level adjustment (5)shown in figure 2. The seed crystal (7) was oriented along a-axis, and the seed crystal (7) is rotated at a speed of 30 rpm for mixing mortar, with the direction of rotation every 3 minutes changed. The initial temperature when grown crystal was equal 842,5°and reducing the temperature was approximately 0.05 to 0.1°C/day. The size of the grown crystal was 51 mm × 35 mm × 25 mm (a-axis × axis × b-axis), the average growth rate was 3.6 mm/day in the direction of a-axis (horizontal direction), the growth period was 14 days, and the weight was equal to 47, the growth Rate and the shape of the crystal were the same as for the standard material for growing the crystals, so it is obvious that the material for growing crystals prepared by mixing starting materials in water the solution according to the present invention, has not had any adverse effects on the growth of the crystal. The scattering in the crystal was investigated using a he-Ne laser, and the result was not detected by light scattering.

Then, to compare the quality of the crystal, obtained from material prepared by mixing in an aqueous solution, with the quality of the crystal obtained from standard material, was measured damage threshold of ultraviolet laser radiation in the following way. From the crystal was cut element in the form of a plate along the C-axis, having a thickness of 1 cm, and both end faces were optically polished. The pulse of laser radiation (wavelength 266 nm, pulse duration 7 NS) has been focusing on the CLBO device using the optical system shown in Fig, and determined the presence or absence of damage. Scratch resistance was determined by the method "1 to 1", each time changing the position of irradiation. The results obtained are shown in Fig. Damage threshold laser crystal (b)derived from the source materials, prepared in the standard way, was equal to 8.8 with 10.4 GW/cm2approximately the same is the damage threshold of fused silica (and) (produced by the company Shin-Etsu Quartz Products Co., Ltd.). Crystal (s)derived from the source materials after initial mixing in the aqueous solution had a damage threshold laser radiation, equal 16,2-of 16.6 GW/cm2that about 1.6 times more damage threshold for fused silica (a), and therefore it is obvious that the crystal is in accordance with the present invention had significantly better resistance to damage by laser radiation, compared with the standard crystal (b). In addition, the crystal (C) had a very narrow interval of the distribution of threshold equal to about 1.0 GW/cm2compared with 3.2 GW/cm2standard crystal (b), which also shows that the homogeneity inside the crystal was improved. It was previously shown that CLBO crystals with a high resistance to damage by laser radiation have a bad dislocation density, so we can conclude that the grown crystal obtained from the original material mixed in aqueous solution, has improved properties.

When growing the crystal melt is stirred by rotation of the crystal and crucible in opposite directions, rotating the blade is immersed in the melt, as shown in Fig. Damage threshold laser crystal obtained in this way is shown in Fig. (a)represents the threshold of damage by laser radiation fused quartz, taken as a comparative example. As can be seen from Fig, crystal (s), grown from material obtained by first mixing the starting materials in an aqueous solution according to the present invention, has a greater homogeneity and resistance to laser radiation than the crystal (b)grown from the original materials prepared standard SP the way.

By infrared absorption spectrometry with Fourier-transform (FT-IR) confirmed that in CLBO-crystal within the crystal structure, there are many IT groups. In addition, in the literature it was reported that the transmittance of ultraviolet radiation decreases with the increase in the number of Oh-groups in the crystal. There was a fear that the crystal grown from the original materials, mixed in aqueous solution, will be included more Oh-groups in comparison with the standard crystal, and therefore, the content of Oh-groups was determined using the method of infrared absorption spectrometry with Fourier-transform (FT-IR). In the literature it was reported that the absorption spectrum of Oh-groups in CLBO-crystal is more clearly expressed in the direction of C-axis than in the direction of a-axis. Therefore, the plate thickness of 1 mm along the C-axis were cut from (a) crystal grown from the original materials prepared in the standard way, and (b) crystal grown from the original material mixed in an aqueous solution, to obtain samples for research. Each crystal was heated to a temperature of 150°C for about 1 day to remove water molecules absorbed on the surface, and then a measurement was performed along the C-axis. The incident infrared radiation was unpolarized. The results are shown in Fig. Maxim what we are about at 3400 cm -1and 3600 cm-1show the absorption associated with HE-groups. From the results it is clear that conventional crystal (a) and crystal (b)derived from the source materials, mixed in aqueous solution, have the same intensity of absorption spectra. Therefore, in the process of evaporation, drying and firing the number of Oh-groups in the powdery source material that is dissolved in water, is reduced to the level of the standard material.

Example 4

Single CLBO crystal obtained by the method according to the present invention was cut into three samples with a length of 10 mm in the direction (Θ,f) = (61,9°, 45°) and optically polished. This angle is the angle of the negotiation phase for the generation of the fourth harmonic of type I for Nd:YAG laser.

The structure of the optical system for measuring threshold internal damage of ultraviolet laser radiation is schematically illustrated Fig. As shown in Fig, as a light source was used Nd : YVO4the laser diode pumped, the pulse repetition frequency was equal 31,25 kHz, and the duration of the output pulses was equal to 10 NS mode SO00. In addition, LBO-crystal type I length of 12 mm was used for the generation of the second harmonic at a high temperature equal to 148°C, non-critical negotiation phases. The first of these CLBO crystals was and is used to generate the fourth harmonic at high temperature, equal to 150°C. Generated thus UV laser (266 nm) focused on the second CLBO-chip (sample), heated to 150°C. the spot Size of the laser beam of the fourth harmonic was approximately equal to 16 microns. The output power of the ultraviolet laser radiation can be changed using the phase difference plate that is controlled by a computer. The measurement was carried out as follows. The output power of the ultraviolet laser radiation was set at 0.6 GW/cm2that was significantly below the threshold of damage, and continuously increased up until the transmittance did not begin to decline rapidly. The threshold was determined as the output intensity, which has led to a rapid decrease of the transmittance (the breakdown).

On Fig shows an example of measurement results of threshold internal damage by laser radiation CLBO crystal heated to 150°With multipulse irradiation. The average value of the threshold internal damage by laser radiation for five sites CLBO crystal was equal to approximately 1.2 GW/cm2. This value is 1 order of magnitude smaller threshold for single-pulse irradiation at a wavelength of 266 nm (approximately 12 GW/cm2).

Pollution CLBO crystal water can be reduced to a certain level by heating to 100°and more in a few days. Accordingly, the change in the degree of pollution of water when heated to 150°the third CLBO crystal, prepared previously, was measured using an indicator of changes in the absorption bands of hydroxyl ion (HE-) by means of an infrared spectrometer with Fourier transform (FT-IR). The absorption bands due to the presence of hydroxyl ions in CLBO-chip, were at about 3400 cm-1and 3600 cm-1so that the absorption spectrum was measured in the range from 3200 to 3800 cm-1every 24 hours up until the change of absorption bands did not stop. The results are shown in Fig. It was confirmed that the intensity of absorption bands at about 3400 cm-1and 3600 cm-1gradually decreases when heated and reaches a plateau after 120 hours.

Threshold internal damage by laser radiation on several sections of the CLBO crystals was measured every 24 hours under the same conditions of heating. The results are shown in Fig. Threshold internal damage by laser radiation has increased gradually when heated and stabilized after about 120 hours. The resulting threshold is approximately 1.35 times the original value. In addition, it was found that a gradual decrease of the transmittance shown in Fig, in the subthreshold range decreased p is increasing time of heating of the crystal.

From these results it is clear that hydroxyl ions, that is, water contamination, associated with nonlinear absorption CLBO crystal, and that the threshold internal damage by laser radiation can be improved by the removal of hydroxyl ions from the CLBO crystal.

Method of removing impurities of hydroxyl ions from the crystal is not limited only by heating, and can be used gassalasca machines, vacuum equipment, etc. or a combination of these methods.

The invention is not limited to the above examples, and obviously can be made a variety of changes details.

Industrial applicability

As described above, according to the present invention includes a new method of obtaining crystals based on borates, in accordance with which at a lower price and in a short period of time to obtain a more uniform and reliable crystal-based borate, which can be used as an optical device for converting the wavelength and the like, and the laser oscillator (laser radiation), in which the crystal is used as an optical device for converting the wavelength.

1. The method of obtaining material for growing crystals based on borate, cesium, including the dissolution of water-soluble soybean is inane cesium and water-soluble boron compounds in water to obtain an aqueous solution, the evaporation of water from the aqueous solution with subsequent sintering or without sintering to obtain material for crystal growth and melting of the material obtained with the aim of growing the crystal on the basis of cesium borate.

2. The method according to claim 1, characterized in that together with the connection of cesium and boron compound dissolved in water a water-soluble compound of at least one of the alkali metals, different from cesium, for growing crystal on the basis of cesium borate with the following gross formula:

CS1-xMxIn3O5,

where M is alkali metal and 0≤x<1.

3. The method of obtaining material for growing crystals on the basis of cesium borate-lithium, including the dissolution of water-soluble compounds of cesium, water-soluble compounds of lithium and water-soluble boron compounds in water to obtain an aqueous solution, the evaporation of water from the aqueous solution with subsequent sintering or without sintering to obtain material for crystal growth and melting of the material obtained with the aim of growing the crystal on the basis of cesium borate-lithium.

4. The method according to claim 3, characterized in that together with the compound of cesium, lithium compound and a boron compound dissolved in water a water-soluble compound of at least one of the alkali metals, different from the cesium and the development, for growing crystal on the basis of cesium borate-lithium with the following gross formula:

Cs1-xLi1-yMx+yIn6About10where x is 0, y<1 or

Cs2(1-z)Li2M2zB12O20where 0<z<1,

and M is alkali metal.

5. The method according to claim 1 or 3, characterized in that the water-soluble compounds of cesium carbonate is a connection.

6. The method according to claim 1 or 3, characterized in that a water-soluble boron compound is boron oxide or boric acid.

7. The method according to claim 1 or 3, characterized in that the aqueous solution is heated to evaporate water.

8. The method according to claim 1 or 3, characterized in that after the evaporation of water from an aqueous solution to produce sintering in the temperature range from 500°and above, but below the melting temperature.

9. The method according to claim 1 or 3, characterized in that the melt material for growing the crystal is stirred during the growing crystal.

10. The method according to claim 1 or 3, characterized in that the grown crystal is heated to reduce contamination of the crystal water.

11. The method according to claim 10, characterized in that the grown crystal is heated to a temperature of 100°C or higher.

12. The method according to claim 10, characterized in that the grown crystal is heated in gossamery atmosphere or under vacuum.

13. The generator of the laser radiation, containing crystal n the basis of Borat, grown from material obtained according to the method as defined in any one of claims 1 to 12, as an optical device for converting the wavelength.



 

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1 tbl, 1 ex

FIELD: chemical industry; methods of growing of volumetric monocrystals.

SUBSTANCE: the invention is dealt with methods of production of volumetric monocrystals and may be used at controlled solution-melt growing of crystals of substances, for example of composite oxides. The device contains a compound cylindrical king-pot system made out of a ceramic material and consisting of the crystallization and auxiliary king-pots linked through a funnel, internal surfaces of which are made with a platinum cover. The crystallization king-pot on its external surface has two ring-type coaxial ledges, the first of which is located on the lower end of its lateral surface, and the second ledge - on the outer diameter of the bottom part of the crystallization king-pot as its extension. The central part of the bottom of the crystallization king-pot is made in the form of the hollow pyramid with the internal surface representing a cone and with its external surface representing a hexahedral pyramid. The furnace system of the king-pot heating is made in the form of three mechanically separated tubular furnace(modules of a planar structure mounted spatially coaxial - sequentially one after another. Autonomous heating elements of tubular furnace modules planar structure are electrically connected each with its power unit and each is supplied with the working temperature sensor and the thermostat. Outputs of the thermostats are connected to the inputs of the unit of the temperature controllers, and outputs of the unit of the temperature controllers are connected to the control inputs of the corresponding power units. Each working temperature sensor is connected to its own thermostat. The unit of temperature controls consists of the similar controllers, the number of which corresponds to the number of the self-contained heaters of the furnace modules. The temperature sensors for control over the temperature of bottoms of the auxiliary and crystallization king-pots are connected to their own thermostats and meters of temperature, and outputs of the temperature controllers and meters of temperature are connected to the computer. The device allows to increase chemical and configuration homogeneity of grown monocrystals at simultaneous decrease of costs of realization of the production processes.

EFFECT: the invention ensures increased chemical and configurational homogeneity of the grown monocrystals at simultaneous decrease of costs of realization of the production processes.

3 cl, 6 dwg

FIELD: Czochralski method for crystal growth from melt, in particular crystals of heat-resistant multicomponent compounds.

SUBSTANCE: single crystal lithium aluminate LiAlO2 is obtained by using Czochralski method in inductive heating equipment. Crystal growth process includes batch melting containing lithium aluminate in iridium crucible followed by single crystal drawing from melt onto oriented seed crystal in inert gas atmosphere. Beforehand prepared batch-cake obtained by compounding of aluminum oxide and lithium carbonate, wherein lithium carbonate excess is 2-4 % in respect to stoichiometric ratio, is used as raw batch. Mixture is heat treated in two steps: at temperature 700oC in the first step and at 1050oC in the second one with holding for 3 h in each step. To prevent losses of volatile batch components crystallization is carried out under excess (not less than 0.3 atm) pressure of inert gas, and at the beginning of growth process broader surface square is screened, seed crystal is grown up to diameter equal to 0.8 of crucible one, then crystal is drawn up to desired length while finished diameter is decreased up to 0.5-0.6 of crucible one. As a result reusable crystal part has form of truncated cone. Single crystal lithium aluminate produced according to present invention is useful in disc production served as substrate in epitaxial film growth, in particular gallium nitride (GaN) films.

EFFECT: coarse-grained crystals of high quality.

1 ex, 1 tbl, 1 dwg

FIELD: technological processes.

SUBSTANCE: invention is related to technology of single crystals LiNbO3 production of stoichiometric composition, which is used in non-linear optics. Single crystals LiNbO3 are melted incongruently, therefore, for production of single crystals of stoichiometric composition, single crystal pulling is used from liquid phase of eutectic composition with make-up of solid phase of preliminarily synthesised compound, which is heated from bottom and top by double-layer spiral electric heater, which is immersed in liquid phase and installed with gap in respect to making-up solid phase, and reduction of temperature gradients in liquid phase and in produced single crystal is performed by application of furnace for single crystal heating. Device includes mechanism of single crystal pulling, thermally insulated crucible with make-up solid phase, flat heater of crucible with thermal insulation, double-layer spiral electric heater with cross-section of spirals in the form of reverse chutes that overlap all section of crucible, which is installed with gap in respect to make-up solid phase, at that double-layer spiral electric heater is equipped with electrodes that pass through furnace thermal insulation for single crystal heating and are fixed to it. Device heaters form flat isothermal surfaces along crucible height, double-layer spiral electric heater with cross section of spirals in the form of reverse chutes that overlap all section of crucible, removes air bubbles that are produced during dissolution of make-up solid phase, from crystallisation front to crucible walls, installation of double-layer spiral electric heater with gap in respect to make-up solid phase provides its heating up to temperature of dissolution provided that temperature gradients in liquid phase and single crystal are reduced, which is achieved by application of furnace with thermal insulation for heating of pulled single crystal, which enters the crucible as make-up dissolves and single crystal is growing.

EFFECT: stabilisation of growth diffusive mechanism performance conditions, reduction of thermal stress in single crystal.

2 cl, 1 dwg

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