A method of producing single crystal tungstate

 

(57) Abstract:

The invention can be used in electronics for the manufacture of scintillators for registration of radiation and worker tel lasers. The inventive growing single crystal tungstate carried out using as a source material of tungsten trioxide and an oxide or carbonate of the divalent metal, tungsten trioxide and an oxide or carbonate of monovalent metal and an oxide of trivalent metal, or tungstate having a molecular formula of XIIWO4or XIXIII(WO4)2where XIdenotes a monovalent metal, XIIis a divalent metal and XIII- trivalent metal, which is formed by heating the above oxides and/or carbonates, and then heated grown tungstate single crystal at a temperature of from 600 to 1550°C in an atmosphere where the partial pressure of oxygen is adjusted so that it is negative with respect to the partial pressure of oxygen in atmospheric air. The method allows to obtain the tungstate single crystal having a high density and a high light emitting intensity, and therefore, suitable as scin is the procedure tungstate single crystal has a high thermal conductivity and, therefore, is suitable as a working body of the laser for two-wavelength laser device. 14 C.p. f-crystals, 1 table.

The technical field

This invention relates to a method for producing a single crystal of tungstate, which can be used as a scintillator for registration of radiation or, as the Raman crystal, as a working body of the laser.

The level of technology

Characteristics of medical equipment, in particular PET (positron emission tomography), quickly improve. As a scintillator for registration of radiation, for example-rays, which is used in PET and so on, require materials with high spatial resolution, in other words, a sufficient density to increase Lokapalas capacity per unit volume. On the other hand, from the point of view of the sensitivity of the measuring device, the increase of the quantity of light (F. E./MeV) (f.E. denotes the photoelectron) increases the accuracy of measurement.

As a material meeting the above requirements, used Bi4Ge3O12. However, to meet the growing demands of materialov, with:

(1) higher density and

(2) a shorter decay time of fluorescence compared to materials currently used.

The table shows the comparative characteristics of different scintillation materials suitable for use in the apparatus of PET, as well as those of scintillation materials, which are usually used in the form of single crystals. To obtain single crystals usually used as source material tungsten trioxide (WO3) and the oxide of the divalent metal, or WO3oxides of monovalent metal and an oxide of trivalent metal; melt the source material, heating it in a platinum crucible in air; and rotate and pull it (Czochralski method).

In the manufacture of equipment PET currently use, for example Bi4Ge3O12, Gd2SiO5:Ce or Lu2SiO5:Ce. Bi4Ge3O12, Gd2SiO5:Ce or Lu2SiO5:Ce emit a large amount of light, but their density is still not high enough; therefore, a material with a higher density. As for CdWO4, although it radiates great if the CT scan (x-ray computed tomography), but not in the equipment PET.

Compared with other wolframate PbWO4has a high density and a small decay time of fluorescence, but with the same intensity of radiation used for exposure, it emits an extremely small amount of light, namely, 1/25 relatively Bi4Ge3O12, 1/50 relatively Gd2SiO5:Ce and 1/188 relatively Lu2SiO5:Ce, making it unsuitable for use in PET. However, in recent years the rapid improvement of the characteristics of the photodiodes used as photodetectors allowed to register even a small amount of light, resulting in a deemed sufficient minimum number of registered light, twice the amount of light emitted from traditional PbWO4that is indicated in the table.

In this regard, there has been a variety of attempts to increase the amount of light emitted from PbWO4and, at the same time, it is better to use the benefits associated with high density and low decay time of fluorescence.

One of the directions of the above studies is that to PbWO4add Mo. However, the addition of Mo to PbWO4may the th radiation the amount of light remains the same as the crystal without additives Mo, and, furthermore, addition of Mo leads to an increase in decay time of fluorescence.

The effect of increasing the amount of emitted light is observed when adding b, Pr, Eu or Sm, each of which is a rare earth element; however, adding this element has a disadvantage in increasing the share of items with a slow decay of fluorescence in the absence of growth of the quantity of light emitted by the elements with fast decay of fluorescence.

Have devised another way to increase the quantity of light, whereby the amount of Cd added to PbWO4, adjust so that the value of X in the molecular formula Pb1-xCdxWO4was in the range of from 0.01 to 0.30, but this method also suffers the disadvantage that in the process of growing and processing of the single crystal increases the likelihood of cracking, which reduces performance.

So far none of these attempts have not led to success in the manufacture of single crystal PbWO4with a small decay time of fluorescence emitting a large amount of light.

On the other hand, involves the Rymer Nd+3and use as Raman crystals, as a working body of the laser. Upon excitation of a working body of the laser using a semiconductor laser or other energy source, receive laser light of two wavelengths, which is light emitted when the Stokes Raman scattering and anti-Stokes Raman scattering, due to the Raman conversion.

Attempts have been made to improve the visible spatial discreteness due to the use of the two-wavelength laser light in the fluorescent microscope and take advantage of the nonlinearity of the luminescence of the dye. Usually, in order to obtain laser light of two wavelengths, uses two lasers operating at different wavelengths, which leads to an increase in the overall size of the fluorescent microscope and higher costs.

Despite the advent of lasers with adjustable wavelength, which allows to obtain laser light of two wavelengths using a single laser, lasers such types of complex and cumbersome due to the mechanical movement of the diffraction grating and a curved plate, which converts the wavelength; therefore, even a laser with adjustable length vanaskie crystals, who can apply for the application as a working body of the laser, include, in addition to PbWO4, a number of monocrystalline wolframates, for example KGd(WO4)2, CdWO4, CaWO4.

However, to be used as a working body of the laser, it is necessary to increase their conductivity. The fact that the accumulation in the crystal, the heat generated during laser operation leads to deformations of the crystal lattice, which causes a change in wavelength generation and optical damage, and, thus, prevents the generation of a continuous wave. In addition, it can be expected that the low conductivity hinders the establishment of working bodies for powerful lasers.

The invention

As described above, so that the single crystal PbWO4can be used as a scintillator for registration of radiation, it is necessary to increase the emitted amount of light. The single crystal PbWO4must emit at least two times more light than conventional single crystal PbWO4. At the same time, to monocrystalline wolframate, for example PbWO4can be used as a working body of the laser, need Powys the task of the invention is to provide a method of producing single crystal tungstate, which emits an increased amount of light without deterioration (increase) decay time of fluorescence, which is suitable for use as a scintillator for registration of radiation in medical equipment, such as PET, and which, moreover, has improved (improved) thermal conductivity and is suitable for use as a working body of the laser for two-wavelength laser device.

A method of producing single crystal tungstate, according to the present invention, characterized in that for single crystal growth of tungstate is used as the source material tungstate having a molecular formula of XIIWO4or XIXIII(WO4)2(where XIdenotes a monovalent metal, XIIis a divalent metal and XIII- trivalent metal), which is obtained by heating the trioxide of tungsten and oxide or carbonate of the divalent metal, tungsten trioxide and an oxide or carbonate of monovalent metal and an oxide of trivalent metal, or these oxides and/or carbonates, and heated grown tungstate single crystal at a temperature of from 600 to 1550°C in an atmosphere where the partial pressure of acid the monocrystal PbWO4usually grown in ambient air. Since oxygen (O) is the basic component of the single crystal PbWO4that is evident from the molecular formula, the concentration of O2in the atmospheric air has a significant influence on the formation of crystal defects in the single crystal. Possibly this is because during the manufacture of the single crystal b partially evaporates from the melt, and crystallizing the crystal formed by Pb4+the exciting O2from the atmosphere to compensate for the reduction of electric charges in Pb2+, which results in a balance of positive and negative ions, in particular, that balance allows you to balance the electric charges WO2-4or (WO2-4+2-) with (Pb2++Pb4+), making of the atomic relations O/N and W/Pb in the crystal deviates from the stoichiometric ratio upwards, causing a large number of lattice defects.

The result of the extensive research on the creation of the single crystal PbWO4that has a smaller decay time fluorescence and emits more light, and monocera. The author of this invention came to the conclusion that the reason for the small amount of light emitted from the single crystal PbWO4and its low thermal conductivity is a large number of lattice defects generated due to the deviation of O/N and W/Pb from the stoichiometric ratio, and eventually found that the single crystal PbWO4should be heated in an atmosphere where the partial pressure of oxygen is adjusted so that it is negative relative to atmospheric air.

It can be assumed that during the heating of the single crystal PbWO4in an atmosphere where the partial pressure of oxygen is adjusted so that it is negative with respect to atmospheric air, the excess Of W contained in the single crystal PbWO4that is emitted from a crystal in the form of O2and WO2and with the release O2and WO2, Pb4+restored to Pb2+thanks monocrystal PbWO4cleared into a single crystal with fewer lattice defects. Under this treatment the color of the single crystal PbWO4changes from transparent yellow to transparent and colorless, which leads to a substantial increase in light transmittance (illusory) education photodiode, designed for Desk light with a wavelength of 400 nm or more. In addition, reducing the number of lattice defects suppresses the decrease in thermal conductivity due to phonon scattering, which allows you to create a good Raman crystal as a working body of the laser.

Although the atmosphere where the partial pressure of oxygen is adjusted so that it is negative with respect to atmospheric air, in General, is an atmosphere where the partial pressure of oxygen is less than 21207 PA at an altitude of 0 m above the ground, to achieve the concentration of O2in which can quickly and reliably to obtain the desired characteristics, the optimum is the partial pressure of oxygen 28 PA or lower. Presumably, the effect will occur even at a partial pressure of oxygen over 28 PA; however, when the oxygen partial pressure exceeds 28 PA, due to a very low rate of diffusion of O and W in the crystal and increase time allocation O2and WO3from the crystal, the performance decreases so that the composition of the atmosphere becomes impractical.

Atmosphere where the partial pressure of oxygen is adjusted so that it alleene) or carbon dioxide (CO2in the atmosphere under atmospheric pressure or reduced pressure in the atmosphere using a vacuum pump. When heated to a temperature of from 600 to 1550°WITH CO2partially decomposes into CO and O2while the equilibrium partial pressure of oxygen is from 0,00059 to 416 PA, and the temperature range in which it is possible to maintain the partial pressure of oxygen 28 PA or less, is from 600 to 1200°C.

When the pressure in the atmosphere using a vacuum pump to remove large amounts of gas (high degree of vacuum) required gas pressure adjustment. As gas pressure adjustment, which allows to achieve a partial pressure of 28 PA or less, can be used not only Ar, N2He and CO2but also the atmospheric air, when the degree of vacuum is adjusted to a value of 130 PA or lower.

When the gas pressure adjustment using hydrogen (H2instead of Ar, N2Not or CO2, PbWO4restored, and the crystal disintegrates.

When you enter Ar, N2Not and CO2the atmosphere at atmospheric pressure and W is diffused from the inside of the crystal is slower than in the case of reducing the pressure in the atmosphere; in resultimage atmospheric gas increases, that leads to increase in cost. Accordingly, in order to reduce the partial pressure of oxygen in the atmosphere, the most beneficial to apply the method, according to which the pressure in the lower atmosphere, adjusting the degree of vacuum to 130 PA or lower. However, when the pressure in the atmosphere to a value less 1×10-2PA increases evaporation PbWO4; therefore, the pressure should be adjusted to output PbWO4.

The heating temperature should be set so that it fell in the range from 600 to 1550°C, whereas the melting point and boiling monocrystalline tungstate, which you want to retrieve.

When the heating temperature below 600°With the speed of diffusion of O and W in the crystal is low, and the allocation of O2and WO3from crystal takes a long time. On the other hand, when the heating temperature above 1550°With almost all wolframate are in the molten state or are dangerously close to melting, because such a temperature close to their melting temperature, which is evident from the following data: CdWO4melts at 1272°C, Bi4Ge3O12- at 1050°C, PbWO4- at 1123°C Gd2SiO5:Ce - at 1900°C, Lu2SiO5:Ce is heated at a temperature of from 600 to 1550°C in the atmosphere, where the partial pressure of oxygen is adjusted to the value that is negative relative to atmospheric air, and then cooled to a temperature of at least 220°C in an atmosphere where the partial pressure of oxygen is adjusted to the value that is negative relative to atmospheric air, Pb2+in PbWO4oxidized in the cooling process, but the transition from Pb2+in Pb4+again can be suppressed. The transition from Pb2+in Pb4+during cooling, for example, up to approximately 350°C, can be suppressed at a partial pressure of oxygen of about 21000 PA to about 300°C is at a partial oxygen pressure of 1013 PA, up to 250°C is at a partial oxygen pressure of 130 PA to about 220°C is at a partial pressure of oxygen of 28 PA. When cooled PbWO4to a temperature below 220°With it can be left in the atmospheric air, since Pb2+oxidizes slowly and almost regardless of the partial pressure of oxygen; however, it is preferable to cool PbWO4to room temperature in an atmosphere where the partial pressure of oxygen is adjusted to the value that is negative relative to atmospheric air.

Although cooling conditions are different for RA is, is acti none of wolframates not runs in the danger adverse effects, resulting in them to have serious defects. The cooling rate is one of the important conditions eliminate thermal deformation, and therefore in the General case should preferably be cooled as slowly as possible with the cooling of the furnace, but differently for each type of crystal.

During heating of the single crystal in an atmosphere where the partial pressure of oxygen is adjusted so that it is negative with respect to atmospheric air, its surface is a little white and turbid; however, thanks to the polishing surface under it appears colorless and transparent smooth surface.

Traditional crystal PbWO4emit the amount of light that is approximately equal to 30 F. E./MeV, whereas the single crystal PbWO4obtained by applying step of heating at a temperature of from 600 to 1100°C in an atmosphere where the partial pressure of oxygen is adjusted so that it is negative with respect to atmospheric air, emit the amount of light that is approximately equal to 60 F. E./MeV or more, which is two times more than in the traditional case. While the decay time fluores,5 to 1.6 W/m·K, that enables us to produce two-wavelength laser device with high performance.

As for the other crystals in addition to single crystal PbWO4then, for example, in the single crystal CdWO4atomic relations Of/CD, W/Cd deviate from the stoichiometric ratio in the direction of increasing, as in the case of the single crystal PbWO4whereas in the case of KGd(WO4)2obtained from oxide of a monovalent metal, divalent metal or trivalent metal having a relatively high boiling point, atomic relations O/(K+Gd) and W/(K+Gd) deviate from the stoichiometric ratio in the direction of decreasing, as in the case of the single crystal CaWO4where the atomic relations O/Sa and W/Ca deviate from the stoichiometric ratio in the direction of decreasing. This can be seen as the cause of a large number of lattice defects.

As for KGd(WO4)2or CaWO4then because their boiling point is lower than that TO2Oh, Gd2O3or Cao, heating in an atmosphere where the partial pressure of oxygen is adjusted so that it is negative with respect to atmospheric air, it is not possible to remove redundant components and, as expected, not thermal voltage, remaining in the single crystal.

Preferred embodiments of the inventions

When receiving, for example, monocrystal PbWO4using as a starting (initial) materials WO3and b or PbWO4Czochralski these materials are melted by heating them in a platinum crucible in air. The PbWO4 crystal can be obtained not only in air but also in the atmosphere of Ar, N2Not or CO2or in an atmosphere of a mixture of these gases with atmospheric air; however, getting in the atmospheric air is preferred from the viewpoint of thermodynamic equilibrium between the single crystal PbWO4and O2, simplify production equipment and reduce costs.

To obtain high-quality single crystal PbWO4you must use the original materials, for example WO3and b containing less impurities in the form of oxides other valences, for example WO2and PbO2. When using PbWO4it should be prepared from WO3and b, as described above. The total number of impurities, preferably, is 1×10-2mol or less per mole PbWO4and, most pre is to the above oxides; however, in the process of making the desired single crystal PbWO4you can use other materials.

Made in this way, the single crystal PbWO4is a very fragile, transparent disc lemon-coloured cylindrical shape. The single crystal PbWO4heated at a temperature of from 600 to 1100°C in an atmosphere of Ar, N2He or CO2or under adjustable pressure, achieving a degree of vacuum of 130 PA or lower, so that the oxygen partial pressure was 28 PA or lower.

In Ar, N2Not or CO2not require a high degree of purity, but it is preferable that the content of O2specified in the analytical table as small as possible. In the case of pressure reduction degree of vacuum, preferably, is 130 PA or lower, and most preferably 5×10-2PA or lower. When the heating of materials in the atmosphere of Ar, N2Not or CO2the flow of such a gas, preferably ranges from 0.5 to 5 l/min; however, it can be changed optionally according to the size of the single crystal, etc. with regard to the heating temperature, it is important to avoid temperatures above 1100°C, since at temperatures exceeding 1100°C, may begin melting MES is Vance; however, in order to reduce the distance that an excessive amount Of and W is held in the crystal, diffundere in the direction of its surface, and to reduce the time of release of these elements from a crystal in the form of O2and WO3before heating the crystal in the appropriate order, it is preferable to cut to proper dimensions. For cutting, you should use a cutting machine with a blade on its inner circumference or saw, because when using these tools on the surface of the slice fewer defects or cracks.

For heating the single crystal PbWO4placed in a platinum boat. Heating time is usually from 12 to 96 hours, depending on the type of atmosphere and size of the crystal. After cooling of the crystal at a temperature of from 600 to 1100°With its cooled down to room temperature for 6-24 hours, maintaining the same composition of the atmosphere.

The single crystal PbWO4that has undergone the above-described heat treatment, cut to a specified size and subjected to mirror polishing. When the irradiation of the thus obtained single crystal PbWO4rays from the source60With the amount of light was 60 F. E./MeV or more, and the decay time of fluorescence remained in PR is the quality of the scintillator. Measuring the conductivity of the crystal at 20°With the method of laser flash got the results from 1.5 to 1.6 bt/m·K. the Results showed a rapid outflow of heat produced by the exciting light radiation.

Let us turn to the description of the examples of this invention.

Example 1

One pray powdered WO3and powdered b, both of which had a purity of 99.99%, weighed and mixed, and the mixed powder material was placed in a platinum crucible with a diameter of 70 mm and a height of 70 mm and melted in ambient air by means of high-frequency heating. From the thus obtained melt using the Czochralski method, received a single crystal PbWO4with a diameter of 35 mm and a length of 65 mm

Then, the single crystal PbWO4placed in a platinum boat, which was heated at a temperature of 950°C for 72 hours in a vacuum oven at a degree of vacuum 5×10-2PA and cooled to room temperature in the same atmosphere for 12 hours.

The single crystal PbWO4that has undergone heat treatment, cut to the size of 1 cm×1 cm×2 cm, was subjected to mirror polishing and irradiated-rays from the source60With from 1 cm thick, measuring the amount of light and more than traditional single crystal PbWO4while the decay time of fluorescence in 10 nanoseconds remained unchanged. In addition, the measured thermal conductivity at 20°With the laser flash. The measurement result was 1.6 W/m·K.

Example 2

The single crystal PbWO4obtained by the Czochralski method, was placed on a platinum boat and heated at a temperature of 1100°C for 48 hours in a vacuum oven at a degree of vacuum 5×10-2PA. The rest of the processing was produced as in example 1.

The single crystal PbWO4that has undergone heat treatment, cut to the size of 1 cm×1 cm×2 cm, was subjected to mirror polishing and irradiated-rays from the source60With from 1 cm thick, measuring the amount of light and the decay time of fluorescence. The measured value of the quantity of light was 72 F. E./MeV, which is about 2.4 times larger than that of conventional single crystal PbWO4while the decay time of fluorescence in 10 nanoseconds remained unchanged. In addition, the measured thermal conductivity at 20°With the laser flash. The measurement result was 1.6 W/m·K.

Example 3

The single crystal PbWO4obtained by the method of Cobra and, maintaining the degree of vacuum of 130 PA by using a pressure regulator and using as gas pressure adjustment the air. The rest of the processing was produced as in example 1.

The single crystal PbWO4that has undergone heat treatment, cut to the size of 1 cm×1 cm×2 cm, was subjected to mirror polishing and irradiated-rays from the source60With from 1 cm thick, measuring the amount of light and the decay time of fluorescence. The measured value of the quantity of light was 60 F. E./MeV, which is about 2.0 times larger than that of conventional single crystal PbWO4while the decay time of fluorescence in 10 nanoseconds remained unchanged. In addition, the measured thermal conductivity at 20°With the laser flash. The measurement result was 1.6 W/m·K.

Example 4

The single crystal PbWO4obtained by the Czochralski method, was placed on a platinum boat and heated at a temperature of 600°C for 96 hours in a vacuum furnace, maintaining the degree of vacuum 5×10-4PA. The rest of the processing was produced as in example 1.

The PbWO4 crystal that has undergone heat treatment, cut to the size of 1 cm×1 cm×2 cm, was subjected to the mirror image is the decay time of fluorescence. The measured value of the quantity of light was 60 F. E./MeV, which is about 2.0 times larger than that of conventional single crystal PbWO4while the decay time of fluorescence in 10 nanoseconds remained unchanged. In addition, the measured thermal conductivity at 20°With the laser flash. The measurement result amounted to 1.5 W/m·K.

Example 5

The single crystal PbWO4obtained by the Czochralski method, was placed on a platinum boat and heated at a temperature of 1100°C for 96 hours in an atmospheric furnace, passing through it AG in which the concentration of O2was < 1. million days, i.e. volumetric million shares (the oxygen partial pressure of 0.1 PA) with a flow rate of 1 l/min. Rest of the processing was produced as in example 1.

The single crystal PbWO4that has undergone heat treatment, cut to the size of 1 cm×1 cm×2 cm, was subjected to mirror polishing and irradiated-rays from the source60With from 1 cm thick, measuring the amount of light and the decay time of fluorescence. The measured value of the quantity of light was 60 F. E./MeV, which is about 2.0 times larger than that of conventional single crystal PbWO4while the decay time of fluorescence in 10 nanoseconds of the rhenium was 1.5 W/m·K.

Example 6

The single crystal PbWO4obtained by the Czochralski method, was placed on a platinum boat and heated at a temperature of 1100°C for 96 hours in an atmospheric furnace, passing through it n2in which the concentration of O2was < 1.million.D. (the oxygen partial pressure of 0.1 PA) with a flow rate of 1 l/min. Rest of the processing was produced as in example 1.

The single crystal PbWO4that has undergone heat treatment, cut to the size of 1 cm×1 cm×2 cm, was subjected to mirror polishing and irradiated-rays from the source60With from 1 cm thick, measuring the amount of light and the decay time of fluorescence. The measured value of the quantity of light was 60 F. E./MeV, which is about 2.0 times larger than that of conventional single crystal PbWO4while the decay time of fluorescence in 10 nanoseconds remained unchanged. In addition, the measured thermal conductivity at 20°With the laser flash. The measurement result amounted to 1.5 W/m·K.

Example 7

The single crystal PbWO4obtained by the Czochralski method, was placed on a platinum boat and heated at a temperature of 1100°C for 96 hours in an atmospheric furnace, introducing into it the gas to shift the territorial pressure of oxygen 28 PA) using a mass flow controller. The rest of the processing was produced as in example 1.

The single crystal PbWO4that has undergone heat treatment, cut to the size of 1 cm×1 cm×2 cm, was subjected to mirror polishing and irradiated-rays from the source60With from 1 cm thick, measuring the amount of light and the decay time of fluorescence. The measured value of the quantity of light was 60 F. E./MeV, which is about 2.0 times larger than that of conventional single crystal PbWO4while the decay time of fluorescence in 10 nanoseconds remained unchanged. In addition, the measured thermal conductivity at 20°With the laser flash. The measurement result amounted to 1.5 W/m·K.

Example 8

One pray powdered WO3and powdered CDO environment, both of which had a purity of 99.99%, weighed and mixed, and the mixed powder material was placed in a platinum crucible with a diameter of 70 mm and a height of 70 mm and melted in ambient air by means of high-frequency heating. From the thus obtained melt using the Czochralski method, received the crystal CdWO4with a diameter of 35 mm and a length of 65 mm

Then, the single crystal CdWO4placed in a platinum boat, which was heated at a temperature of 1150°C in the atmosphere for 24 hours.

The single crystal CdWO4that has undergone heat treatment, cut to the size of 1 cm×1 cm×2 cm, was subjected to mirror polishing and irradiated-rays from the source60With from 1 cm thick, measuring the amount of light and the decay time of fluorescence. The measured value of the quantity of light was 4275 F. E./MeV, which is approximately 1.5 times larger than that of conventional single crystal CdWO4while the decay time fluorescence 5000 nanoseconds remained unchanged. In addition, the measured thermal conductivity at 20°With the laser flash. The measurement result was 2.9 W/m·K.

Example 9

Two mole of powdered WO3one mol of powdered2CO3and one mol of powder CD2ABOUT3who all had a purity of 99.99%, weighed and mixed, and the mixed powder material was placed in a platinum crucible with a diameter of 70 mm and a height of 70 mm and melted in ambient air by means of high-frequency heating. From the thus obtained melt using the Czochralski method, received the crystal KGd(WO4)2with a diameter of 30 mm and a length of 35 mm

Then, the single crystal KGd(WO4)2placed in a platinum boat, which was heated at the same time atoi temperature in the same atmosphere for 24 hours.

Irradiation of the single crystal-rays from the source60With KGd(WO4)2gave such a small amount of light that it didn't recognize a good scintillation material, so measure the amount of light is not conducted.

The single crystal KGd(WO4)2that has undergone heat treatment, cut to the size of 1 cm×1 cm×2 cm, and measured thermal conductivity at 20°With the laser flash. The conductivity increased to 1.7 W/m·compared to 1.6 W/m·for traditional KGd(WO4)2.

Example 10

One pray powdered WO3and powdered Cao, both of which had a purity of 99.99%, weighed and mixed, and the mixed powder material was placed in a platinum crucible with a diameter of 70 mm and a height of 70 mm and melted in ambient air by means of high-frequency heating. From the thus obtained melt using the Czochralski method, received the crystal CaWO4with a diameter of 30 mm and a length of 40 mm

Then, the single crystal CaWO4placed in a platinum boat, which was heated at a temperature of 1550°C for 72 hours in a vacuum oven at a degree of vacuum of 0.1 PA and cooled to room temperature in the same atmosphere for 24 h;2 cm, was subjected to mirror polishing and irradiated-rays from the source60With from 1 cm thick, measuring the amount of light and the decay time of fluorescence. The measured value of the quantity of light amounted to 2000 F. E./MeV, which is about 1.1 times greater than traditional single crystal CaWO4while the decay time fluorescence 5000 nanoseconds remained unchanged. In addition, the measured thermal conductivity at 20°With the laser flash. The measurement result was 2.5 W/m·K.

Industrial applicability

In accordance with the above-described method of producing single crystals of tungstate, corresponding to this invention allows to obtain single crystals of tungstate having a high density and produce an increased amount of light, which allows their use as scintillators for registration of radiation, in particular x-rays or-rays and, in addition, has high thermal conductivity, which allows their use as working fluids lasers for two-wavelength laser devices.

1. A method of producing single crystal tungstate, characterized in that it contains the steps that are grown single crystal tungstate from wolfra who appoints monovalent metal, XIIis a divalent metal and XIII-trivalent metal), which is obtained by heating the trioxide of tungsten oxide or carbonate of the divalent metal trioxide of tungsten oxide or carbonate of monovalent metal and an oxide of trivalent metal or oxides and/or carbonates, and heated grown tungstate single crystal at a temperature of from 600 to 1550°C in an atmosphere where the partial pressure of oxygen is adjusted so that it is negative relative to atmospheric air.

2. A method of producing single crystal tungstate under item 1, characterized in that the partial pressure of oxygen in the atmosphere is adjusted so that it is negative with respect to atmospheric air, through the introduction into the atmosphere of argon, nitrogen, helium or carbon dioxide at atmospheric pressure.

3. A method of producing single crystal tungstate under item 1 or 2, characterized in that the partial pressure of oxygen in the atmosphere is adjusted so that it is negative with respect to atmospheric air, by reducing the pressure in the atmosphere to 130 PA or lower by using a vacuum pump.

4. A method of producing single crystal tungstate under item 1 or 2, on the receipt of a single crystal of tungstate on p. 3, characterized in that the partial pressure of oxygen in the atmosphere is 28 PA or lower.

6. A method of producing single crystal tungstate under item 1 or 2, characterized in that it further comprises a stage on which cool the grown single crystal of tungstate to 220°C or higher in an atmosphere where the partial pressure of oxygen is adjusted so that it is negative with respect to atmospheric air, after heating of tungstate single crystal at a temperature of from 600 to 1550°C in an atmosphere where the partial pressure of oxygen is adjusted so that it is negative relative to atmospheric air.

7. A method of producing single crystal of tungstate on p. 3, characterized in that it further comprises a stage on which cool the grown single crystal of tungstate to 220°C or higher in an atmosphere where the partial pressure of oxygen is adjusted so that it is negative with respect to atmospheric air, after heating of tungstate single crystal at a temperature of from 600 to 1550C in an atmosphere where the partial pressure of oxygen is adjusted so that it is negative relative to atmospheric air.

8. A method of producing single crystal of voltra is ultramate to 220°C or higher in the atmosphere, where the partial pressure of oxygen is adjusted so that it is negative with respect to atmospheric air, after heating of tungstate single crystal at a temperature of from 600 to 1550°C in an atmosphere where the partial pressure of oxygen is adjusted so that it is negative relative to atmospheric air.

9. A method of producing single crystal of tungstate on p. 5, characterized in that it further comprises a stage on which cool the grown single crystal of tungstate to 220°C or higher in an atmosphere where the partial pressure of oxygen is adjusted so that it is negative with respect to atmospheric air, after heating of tungstate single crystal at a temperature of from 600 to 1550°C in an atmosphere where the partial pressure of oxygen is adjusted so that it is negative relative to atmospheric air.

10. A method of producing single crystal tungstate under item 1 or 2, characterized in that the tungstate single crystal is a single crystal of lead tungstate.

11. A method of producing single crystal of tungstate on p. 3, wherein the tungstate single crystal is a single crystal of lead tungstate.

12. With the t of a single crystal of lead tungstate.

13. A method of producing single crystal of tungstate on p. 5, wherein the tungstate single crystal is a single crystal of lead tungstate.

14. A method of producing single crystal of tungstate on p. 6, wherein the tungstate single crystal is a single crystal of lead tungstate.

15. A method of producing single crystal of tungstate on p. 7, 8 or 9, characterized in that the tungstate single crystal is a single crystal of lead tungstate.



 

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The invention relates to the field of processing (refining) of the diamond to give them a different color colouring and may find application in the jewelry industry

The invention relates to the field of obtaining single crystals of ferroelectric domain structure formed and can be used when creating and working appliances precise positioning, in particular probe microscopes, as well as during alignment optical systems

The invention relates to methods of obtaining crystals, namely the method of producing single crystals of lead tungstate, and can be used in the manufacture of scintillation elements

The invention relates to optoelectronics nuclear physics research, but rather making a powerful solid-state lasers operating in the UV region of the spectrum
The invention relates to the field of processing of diamonds

The invention relates to a technology of manufacturing products of mono - or polycrystalline samples used in nuclear and space technology, medical diagnostics and other fields of science and technology for registration of ionizing radiation

The invention relates to methods of obtaining crystals, namely the method of producing single crystals of lead tungstate, and can be used in the manufacture of scintillation elements

The invention relates to methods of obtaining crystals, namely the method of producing single crystals of lead tungstate, and can be used in the manufacture of scintillation elements used in the detectors of ionizing radiation, high energy, working in conditions of high doses in tracts registration requiring high time resolution

The invention relates to methods of obtaining crystals, namely the method of producing single crystals of lead tungstate (hereinafter PWO), and can be used in the manufacture of scintillation elements used in the detectors of ionizing radiation, high energy, working in conditions of high doses in tracts registration requiring high time resolution

Laser substance // 2066352
The invention relates to the field of quantum electronics and can be used in the development of lasers in the infrared range

The invention relates to techniques for registration and spectrometry of ionizing radiation, in particular for scintillation materials

The invention relates to materials and can be used to create managed functional devices

The invention relates to the field of scintillation materials used for registration and spectroscopie ionizing radiation

The invention relates to the field of growing single crystals from the melt and can be used to create a device for growing single crystals of sapphire

The invention relates to growing silicon single crystals by the Czochralski method, in particular to devices for re-loading of material into the crucible, and can be used on plants growing single crystals of silicon, equipped with a gateway device to provide semi-continuous growing single crystals

The invention relates to the field of obtaining single crystals of semiconductor materials and can be used to obtain silicon single crystal by Czochralski method
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