Polarisation method of monocrystal of lithium tantalate

FIELD: metallurgy.

SUBSTANCE: invention relates to industrial production of monocrystals, received from melt by Czochralski method, and can be used during polarisation of ferroelectrics with high temperature Curie, principally lithium tantalate. On monocrystal of lithium tantalate by means of grinding it is formed contact pad, surface of which is perpendicular to optical axis of crystal or at acute angle to it. Monocrystal is located between bottom segmental or laminar platinum electrode and implemented from wire of diametre 0.3-0.6 mm top circular platinum electrode through adjoining to its surfaces interlayers. In the capacity of material of interlayer it is used fine-dispersed (40-100 mcm) powder of crystalline solid solution LiNb1-xTaxO3, where 0.1≤x≤0.8, with bonding alcoholic addition in the form of 94-96% ethyl alcohol at mass ratio of alcohol and powder 1:2.5-3.5. Monocrystal is installed into annealing furnace, it is heated at a rate not more than 70°C/h up to temperature for 20-80°C higher than temperature Curie of monocrystal and through it is passed current by means of feeding on electrodes of polarising voltage. Then monocrystal is cooled in the mode current stabilisation at increasing of voltage rate 1.2-1.5 times up to temperature up to 90-110°C lower than temperature Curie, and following cooling is implemented in the mode of stabilisation of polarising voltage at reduction of current value through monocrystal. At reduction of current value 3.0-4.5 times of its stable value voltage feeding is stopped, after what monocrystal is cooled at a rate of natural cooling-down. Monocrystal cooling up to stop of feeding of polarising voltage is implemented at a rate 15-30°C/h.

EFFECT: method provides increasing of efficiency of monocrystals polarising of lithium tantalate, different by orientation, dimensions and conditions of growing; shaped interlayer provides durable and uniform cohesion of crystal surface to electrodes, and current and voltage stabilisation and fixed rate of crystal cooling in the range of temperature Curie provide guaranteed receiving of transparent, blast-furnace crystals of lithium tantalite without additional defects in the form of cracks and disruptions.

3 cl, 4 ex

 

The invention relates to the production of single crystals grown from the melt by Czochralski method, and can be used for polarization of the ferroelectric with a high Curie temperature, mainly that of lithium tantalate.

When using ferroelectric single crystals in electronic engineering is a prerequisite monodominant crystal, i.e. the same direction of the vector of spontaneous polarization in the whole volume of the crystal. Feature dielectric ferroelectrics, in particular that of lithium tantalate, are the small size of the domains and the low conductivity of the single crystal at a temperature of phase transition of the second kind. Therefore, when the polarization of the lithium tantalate there is a problem of application of high voltage for transfer of large single crystals in monodominance state. In addition, the electrical conductivity of single crystals of lithium tantalate, obtained from the melt by Czochralski method, essentially depends on the chemical composition of tooling due to partial dissolution of the material of the crucible into the melt, and form inert atmosphere. To achieve effective polarization requires a differentiated approach to the choice of the electrical parameters of the mode monogamously - voltage and current, as well as ensuring uniform application the Oia electric field and strong coupling between the electrodes and the surface of the pads through the intermediate layers.

The known method of polarization of the single crystal of lithium tantalate (see application 1-172299 Japan, IPC4SW 33/00, 1987), including the placement of a single crystal of lithium tantalate, grown by Czochralski method in the direction perpendicular to the optical axis of the crystal between a pair of platinum electrodes using intermediate layers of monocrystalline powder lithium niobate LiNbO3or SPECA having greater conductivity at T>650°C, polarizable than the single crystal, and do not interact with him in a chemical reaction, and the imposition of a polarizing voltage to the electrodes.

The disadvantage of this method is the limited temperature range in which the intermediate layers between the crystal and the electrodes have high conductivity, as well as insufficient adhesion of the intermediate layer with the surface of the crystal and the electrodes, which reduces the efficiency of polarization of single crystals. Taking into account the specifics of receipt of the polarizable crystals of lithium tantalate method can only be applied to single crystals with a specific direction of cultivation.

Known also adopted as a prototype, the way the polarization of the single crystal of lithium tantalate (see U.S. Pat. 2046163 RF, MPK6SW 33/04, 1995), including the formation of the single crystal grown by the Czochralski method, the contact area and, surface of which is parallel generatrix of the cylindrical surface of the crystal and is the angle between the normal to the pad and the optic axis of the crystal is not more than 40°, placing the crystal in a furnace horizontally between the upper plate and lower segmental platinum electrodes contact the ground up using the adjacent intermediate layer thickness of 0.5-1.0 mm from a powder of lithium niobate with a particle size of not more than 0.1 mm, heating the crystal up to the Curie temperature with a speed of 100-120°C/h, the feed crystal fixed polarizing voltage, the value of which set the rate of 10 To 1 mm diameter crystal, while cooling monocrystal with the speed of the natural cooling of the furnace.

The disadvantages of this method are that the voltage applied to the crystal, is a fixed value and it is chosen only with regard to the size of the crystal. When cooled dielectric single crystal of lithium tantalate of the Curie temperature with the rate of natural cooling of the furnace and at a fixed voltage value is relatively rapid decrease in current. To limit this process, the voltage applied to the crystal, should be obviously more necessary to implement the reorientation of domains, which can lead to RA is cresciani crystal or does not provide complete monogamously ferroelectric crystal. This reduces the efficiency of the process. In the known method does not provide the means for fixing the powder of the intermediate layer of lithium niobate, which prevents the formation of a strong and uniform contact with thermoelectrode. In addition, the range of operating temperatures, the powder of the lithium niobate has a lower conductivity than tantalate lithium, which also reduces the effectiveness of monodominance.

The present invention is directed to the achievement of the technical result consists in increasing the efficiency of polarization of single crystals of lithium tantalate at the expense of increasing the strength and uniformity of the adhesion of the surface of the single crystal with electrodes and control of electrical parameters during cooling monodimensional crystal.

The problem is solved in that in the method of the polarization of the single crystal of lithium tantalate, including the formation of contact pads, the surface of which is perpendicular to the optical axis of the crystal or to have an acute angle, placing the crystal between the upper and lower platinum electrodes using the adjacent intermediate layers based on lithium niobate, heating of the single crystal, the transmission through it of an electric current by submitting to the electrodes polarizing voltage and cooling of the single crystal is about the rate of natural cooling, according to the invention as a material of the intermediate layer using the fine powder of the crystalline solid solution LiNb1-xTaxO3where is 0.1≤x≤0.8, the binder with alcohol additive, heating of the single crystal lead at a speed of not more than 70°C/h until the temperature of 20-80°C. above the Curie temperature of the single crystal, the cooling of the single crystal lead to the stabilization mode current with increasing voltage 1.2-1.5 times to a temperature of 90-110°C below the Curie temperature, further cooling of the single crystal lead to the stabilization mode polarizing voltage while reducing the magnitude of the current through the crystal and by reducing the magnitude of the current in the 3.0-4.5 times from its stable value when a voltage is stopped, after which the single crystal is cooled with the rate of natural cooling, with the cooling of the single crystal to stop the flow polarizing voltage lead with the speed of 15-30°C/h

The achievement of the technical result is driven by the fact that the use of powder crystalline solid solution with a particle size of 40-100 μm, and as a binder added spirit take 94-96% ethyl alcohol in a mass ratio of powder of solid solution 1:2,5-3,5.

The achievement of the technical result also contributes to the fact that the upper platinum electrode is made of the annular about Aoki diameter of 0.3-0.6 mm

The essential features of the claimed invention, defining the scope of legal protection and sufficient to obtain the above-mentioned technical result function and correlate with the results as follows.

Using as the material of the intermediate layer of fine polycrystalline powder of solid solution LiNb1-xTaxO3(0,1≤x≤0,8) with binder alcohol additive allows to form a uniform intermediate layer, which in the temperature range of monodominance lithium tantalate korrektiruete and provides strong adhesion with the electrode material and the surface of the single crystal. The thickness of the layer when it is chosen in such a way as to prevent cracking of the single crystal due to the contact with platinum. The greater the electrical conductivity of polycrystalline powder of solid solution LiNb1-xTaxO3(or 0.1≤x≤0.8) is compared with the powder of the lithium niobate provides a more "soft" mode of conducting the process.

Conduction heating of the single crystal at a speed of not more than 70°C/h due to the fact that tantalate lithium is the pyroelectric crystal and has a tendency to crack with a sharp temperature drop. When such a heating rate provides a smooth and uniform heating of the single crystal p is throughout its volume.

Heating of the single crystal at the above rate until the temperature of 20-80°C. above the Curie temperature of the single crystal, which, depending on the ratio of Li/Ta is 640-680°C, allows you to put the crystal in paraelectricity nonpolar phase and reach a temperature of compacting the material of the intermediate layer. The transition of the crystal in the ferroelectric phase during cooling and the presence of an electric field leads to the orientation of the vector of spontaneous polarization of each domain in a given field direction.

The cooling of the single crystal in the stabilization mode current can provide monogamously dielectric single crystal of lithium tantalate in terms of a uniform electric field at the initial stage of cooling. According to the invention this is achieved by applying connected in series standard sources of DC power. The amount of current through the crystal set depending on the crystal orientation and dimensions of the contact area, while the initial voltage increase by 1.2-1.5 taking into account the electrophysical properties of each individual crystal to provide current regulation during cooling of the crystal, which avoids cracking of the crystals and ensures the completeness of the passing of monodominance.

The cooling of the single crystal to t is mperature at 90-110°C below the Curie temperature in the stabilization mode current allows to ensure the completeness of monodominance in terms of a uniform electric field and to exclude the appearance of regions of the single crystal with residual predominantly.

Further cooling of the single crystal in the stabilization mode polarizing voltage while reducing the magnitude of the current through the crystal allows you to maintain established the direction of the vector of spontaneous polarization domains until excluding their reorientation.

A decrease in the current 3.0-4.5 times from its stable value upon cooling indicates completion of the process of monodominance and further application polarizing voltage is unreasonable.

The cooling of the single crystal with the speed of natural cooling after cessation polarizing voltage contributes to a gradual lowering of the temperature in the furnace of the single crystal to room and ensures its integrity during processing.

Lowering the temperature of the single crystal with the speed of 15-30°C/h to stop the flow polarizing voltage is necessary because it provides a smooth and uniform cooling of the single crystal throughout the volume, and uniformity of the electric field in the stabilization mode current, and elimination of cracking of the single crystal in the cooling mode voltage regulation.

The combination of the above features is necessary and sufficient to achieve the technical result of the invention, the sign is eghosa in increasing the efficiency of polarization of single crystals of lithium tantalate at the expense of increasing the strength and uniformity of the adhesion of the surface of the single crystal with electrodes and regulation of electrical parameters in cooling monodimensional crystal.

In some cases, of the preferred embodiment of the invention the following specific operations and operational parameters.

Using the powder of the solid solution particle size of 40-100 μm due to the need for structurally homogeneous intermediate layer during its compaction.

The use of alcohol as a binder additive 94-96% ethanol allows you to form a homogeneous intermediate layer of specified geometry and thickness, and promotes the most robust associations between fine particles of crystalline powder of solid solution LiNb1-xTaxO3.

The use of alcohol binder additives in the mass ratio of the powder of solid solution 1:2,5-3,5 allows you to get the consistency of the material of the intermediate layer providing the desired viscosity and adhesiveness of the layer.

Perform upper platinum electrode annular wire diameter of 0.3 to 0.6 mm allows in combination with the intermediate layer formed on the contact pad of the single crystal, to provide the necessary conditions for uniform electric field distribution at the plane of contact pads, respectively, in the crystal volume, and reduce the cost of using deficit is on the precious metal.

The above private features of the invention allow a method in the optimal mode from the viewpoint of obtaining high technological parameters of the process.

The method according to the invention is as follows. On the single crystal of lithium tantalate by grinding to form a contact pad, the surface of which is perpendicular to the optical axis of the crystal or to have an acute angle. Prepare the material of the intermediate layer in the form of a dense suspension of fine (40-100 μm) powder crystalline solid solution LiNb1-xTaxO3where is 0.1≤x≤0.8, the binder and an alcohol additive - 94-96% ethyl alcohol when the mass ratio of the powder of solid solution 1:2,5-3,5. The crystal set in the annealing furnace contact area up to adjacent to the lower segmental plate or electrode is uniformly formed intermediate layer to a thickness of 3-5 mm On the surface of the pads also form an intermediate layer, put the top annular electrode (round or oval), made of platinum wire with a diameter of 0.3-0.6 mm, and press the single-crystal puck from tantalate or lithium niobate weight of about 200, While the single crystal is placed between the negative and lower positive upper electr who DAMI through adjacent to the surface of the intermediate layers. During heating of the single crystal and passing through it an electric current to evaporate the binder and the intermediate layer korrektiruete, providing a secure grip of the single crystal platinum electrodes. Heat lead with a speed of not more than 70°C/h until the temperature of 20-80°C. above the Curie temperature of the single crystal, in which through the crystal electric current is passed. The magnitude of the current source DC power supply B5-50 set depending on the size of the crystal: diameter and length of the cylindrical part. Gradually increasing the voltage of the power source, determine its minimum value needed to transfer power source in the stabilization mode current. Then the voltage source increases by 1.2-1.5 times its minimum value, taking into account features of single crystal growth and material used crucibles (Ir, PtRh 30 with the inner platinum liner etc). Polarization leads, cooling the single crystal with the speed of 15-30°C/h to a temperature of 90-110°C below the Curie temperature, first in the stabilization mode current, and then the cooling with the same speed - mode voltage. When reducing a residual current of 3.0-4.5 times from its stable value flow polarizing voltage drop, after which the single crystal is cooled with what speed the natural cooling to room temperature.

The essence of the invention and its advantages can be explained by the following examples of specific performance.

Example 1. Take the single crystal of lithium tantalate with a diameter of 76 mm and a length of the cylindrical part 80 mm, grown by Czochralski method in the direction of the X axis using the iridium crucible. By grinding to form a contact pad, the surface of which is perpendicular to the optical axis of the crystal and parallel generatrix of the cylindrical part. Prepare the material of the intermediate layer in the form of a dense suspension of the powder of the crystalline solid solution LiNbfor 0.6Tafor 0.4O3particle size 40-60 μm and 96% ethyl alcohol as a binder additive when the mass ratio of alcohol powder and 1:3. On the lower segmental (negative) electrode placed in the annealing furnace, to form the intermediate layer of the suspension with a thickness of 5 mm and install the single crystal contact area up. On the surface of the pads also form an intermediate layer with a thickness of 5 mm, place the top circle (positive) electrode of platinum wire with a diameter of 0.5 mm and pressed a single crystal plate of lithium tantalate weight of 200, Carry out heating of the single crystal at 40°C/h to a temperature of 740°C (60°C. above the Curie temperature), when reaching the cat who swarm through the crystal passed an electrical current of 5 mA at a voltage of 520 V, which corresponds to the minimum value needed to transfer power source in the stabilization mode current. Gradually increase the polarization voltage to 780 In (1.5 times). The intermediate layer thus korrektiruete, providing a secure grip of the single crystal with electrodes. Polarization lead to the stabilization mode current, cooling the single crystal at 25°C/h to a temperature of 590°C (90°C below the Curie temperature) switching power supply mode voltage. Upon further cooling at 25°C/h and decrease the current to the value of 1.7 mA (3 times from its stable value), which corresponds to a temperature of 560°C, the flow polarizing voltage drop, after which the single crystal is cooled with a rate of natural cooling to room temperature. Polarized single crystal of lithium tantalate visual inspection is transparent, has no defects such as cracks and breakouts. In the control of polarized single crystal by the nature of the scattering of the laser beam passing through the crystal, it was found that the crystal is a mono-domain.

Example 2. Take the single crystal of lithium tantalate with a diameter of 80 mm with the length of the cylindrical part 60 mm, grown by Czochralski method in the direction of the X axis using a platinum-rhodium crucible (alloy PtRh30) in the morning platinum liner. By grinding to form a contact pad, the surface of which is perpendicular to the optical axis of the crystal and parallel generatrix of the cylindrical part. Prepare the material of the intermediate layer in the form of a dense suspension of the powder of the crystalline solid solution LiNbfor 0.3Ta0,7O3the particle size of 40-80 μm and 96% ethyl alcohol as a binder additive when the mass ratio of alcohol and powder of 1:3.5. On the lower segmental (negative) electrode placed in the annealing furnace, to form the intermediate layer of the suspension with a thickness of 5 mm and install the single crystal contact area up. On the surface of the pads also form an intermediate layer with a thickness of 5 mm, place the top circle (positive) electrode of platinum wire with a diameter of 0.6 mm and pressed a single crystal plate of lithium tantalate weight of 200, Carry out heating of the single crystal at a speed of 60°C/h to a temperature of 760°C (80°C. above the Curie temperature), at which time via a single pass electric current of 6 mA at a voltage of 490 In that it corresponds to the minimum value required to transfer power source in the stabilization mode current. Gradually increase the polarization voltage up to 690 V (1.4 times). Intermediate layer in this compact shall I, providing a secure grip of the single crystal with electrodes. Polarization lead to the stabilization mode current, cooling the single crystal at a rate of 20°C/h to a temperature of 570°C (110°C below the Curie temperature) switching power supply mode voltage. Upon further cooling rate of 20°C/h and decrease the current to the value of 1.3 mA (4.5 times from its stable value), which corresponds to a temperature of 550°C, flow polarizing voltage drop, after which the single crystal is cooled with a rate of natural cooling to room temperature. Polarized single crystal of lithium tantalate visual inspection is transparent, has no defects such as cracks and breakouts. In the control of polarized single crystal by the nature of the scattering of the laser beam passing through the crystal, it was found that the crystal is a mono-domain.

Example 3. Take the single crystal of lithium tantalate with a diameter of 84 mm and a length of the cylindrical part 59 mm, grown by Czochralski method in the direction of the Y-axis,+36° C using a platinum-rhodium crucible (alloy PtRh30) with internal platinum liner. By grinding to form a contact pad, the surface of which is perpendicular to the axis of cultivation and has an acute angle with the optical axis of the crystal. Prepare the material of the intermediate layer is a thick suspension of the powder of the crystalline solid solution LiNb of 0.2Ta0,8O3size 60-100 micron and 94% of ethyl alcohol as a binder additive when the mass ratio of alcohol and powder of 1:3.5. On the bottom plate (negative) electrode placed in the annealing furnace, forming an intermediate layer from a suspension of 4 mm thickness and install the single crystal contact area up. On the surface of the pads also form an intermediate layer with a thickness of 4 mm, place the top circle (positive) electrode of platinum wire with a diameter of 0.3 mm and pressed a single crystal plate of lithium tantalate weight of 200, Carry out heating of the single crystal at 50°C/h to a temperature of 720°C (40°C above the Curie temperature), at which time via a single pass electric current of 10 mA at a voltage of 681 In that it corresponds to the minimum value required to transfer power source in the stabilization mode current. Gradually increase the polarization voltage up to 885 In (1.3 times). The intermediate layer thus korrektiruete, providing a secure grip of the single crystal with electrodes. Polarization lead to the stabilization mode current, cooling the single crystal with a speed of 15°C./h to a temperature of 580°C (100°C below the Curie temperature) switching power supply mode voltage. When Yes is ineichen cooling at 15°C/h and decrease the current to the value of 2.2 mA (4.5 times from its stable value), which corresponds to a temperature of 560°C, the flow polarizing voltage drop, after which the single crystal is cooled with a rate of natural cooling to room temperature. Polarized single crystal of lithium tantalate visual inspection is transparent, has no defects such as cracks and breakouts. In the control of polarized single crystal by the nature of the scattering of the laser beam passing through the crystal, it was found that the crystal is a mono-domain.

Example 4. Take the single crystal of lithium tantalate with a diameter of 82 mm, a length of the cylindrical part 61 mm, grown by Czochralski method in the direction of the Y-axis,+36° using the iridium crucible. By grinding to form a contact pad, the surface of which is perpendicular to the axis of cultivation and has an acute angle with the optical axis of the crystal. Prepare the material of the intermediate layer in the form of a dense suspension of the powder of the crystalline solid solution LiNbfor 0.9Taa 0.1O3the particle size of 40-100 μm and 94% of ethyl alcohol as a binder additive when the mass ratio of alcohol and powder of 1:2,5. On the bottom plate (negative) electrode placed in the annealing furnace, forming an intermediate layer from a suspension of 3 mm thickness and install the single crystal contact area up. On the surface pads changeformat intermediate layer of a thickness of 3 mm, place the top circle (positive) electrode of platinum wire with a diameter of 0.3 mm and pressed a single crystal plate of lithium tantalate weight of 200, Carry out heating of the single crystal with a speed of 70°C/h to a temperature of 700°C (20°C above the Curie temperature), at which time via a single pass electric current of 14 mA at a voltage of 430, which corresponds to the minimum value needed to transfer power source in the stabilization mode current. Gradually increase the polarization voltage up to 516 In (1.2 times). The intermediate layer thus korrektiruete, providing a secure grip of the single crystal with electrodes. Polarization lead to the stabilization mode current, cooling the single crystal at a speed of 30°C./h to a temperature of 590°C (90°C below the Curie temperature) switching power supply mode voltage. Upon further cooling at 30°C/h and decrease the current to a value of 3.5 mA (4 times from its stable value), which corresponds to a temperature of 560°C, the flow polarizing voltage drop, after which the single crystal is cooled with a rate of natural cooling to room temperature. Polarized single crystal of lithium tantalate visual inspection is transparent, has no defects as is resin and breakdowns. In the control of polarized single crystal by the nature of the scattering of the laser beam passing through the crystal, it was found that the crystal is a mono-domain.

From the above Examples 1-4 shows that the proposed method compared with the prototype to improve the efficiency of polarization of single crystals of lithium tantalate, obtained by the Czochralski method and differing in orientation, size and growing conditions. Forming the intermediate layer provides a strong and uniform adhesion of the crystal surface with the electrodes, and the stabilization of current, voltage and the fixed cooling rate of the crystal in the region of the Curie temperature allow guaranteed to get transparent, mono-domain crystals of lithium tantalate without additional defects such as cracks and breakouts. The method can be applied for the polarization of a wide class of single crystals on the basis tantalate and lithium niobate, is relatively simple and is implemented using standard equipment.

1. The method of polarization of the single crystal of lithium tantalate, including the formation of contact pads, the surface of which is perpendicular to the optical axis of the crystal or to have an acute angle, placing the crystal between the upper and lower platinum electrodes using adjacent Prohm is filling layers based on lithium niobate, heating of the single crystal, the transmission through it of an electric current by submitting to the electrodes polarizing voltage and cooling of the single crystal with the speed of natural cooling, characterized in that the material of the intermediate layer using the fine powder of the crystalline solid solution
LiNb1-xTaxO3where is 0.1≤x≤0.8, the binder with alcohol additive, heating of the single crystal lead at a speed of not more than 70°C/h until the temperature of 20-80°C. above the Curie temperature of the single crystal, the cooling of the single crystal lead to the stabilization mode current with increasing voltage 1.2-1.5 times to a temperature of 90-110°C below the Curie temperature, further cooling of the single crystal lead to the stabilization mode polarizing voltage while reducing the magnitude of the current through the crystal and by reducing the magnitude of the current in the 3.0-4.5 times from its stable value when a voltage is stopped, after which the single crystal is cooled with the rate of natural cooling, with the cooling of the single crystal to stop the flow polarizing voltage lead with the speed of 15-30°C/h

2. The method according to claim 1, characterized in that use powder crystalline solid solution with a particle size of 40-100 μm, and as a binder added spirit take 94-96%ethanol (in mass ratio is Oseni powder of solid solution 1:2,5-3,5.

3. The method according to claim 1, characterized in that the upper platinum electrode is made of a ring-shaped wire diameter of 0.3 to 0.6 mm



 

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5 cl, 2 ex, 2 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

FIELD: processes and devices for growing optical crystals designed for optic-electronic apparatuses.

SUBSTANCE: device includes housing with growing chamber and with cooling chamber mutually divided by means of ceramic partition, crucible arranged in growing chamber, induction heater, upper metallic heating shield mounted over crucible, mechanism with rod for moving crystal. Crucible is in the form of cylinder whose flat bottom is joined with cylindrical lateral surface along spherical surface. Metallic upper shield has two sections, lower cone section and upper spherical section. Between chamber for growing and chamber for cooling diaphragm with changeable concentric inserts is arranged. Induced Foucault current detector in the form of cylinder is mounted on bottom part of crucible. Inner diameter of any concentric insert of said diaphragm exceeds by 2 - 16 mm diameter of grown crystal. Concentric inserts of diaphragm are made of crucible material. Relation of height of cylindrical wall of crucible to height of wall of induced Foucault current detector is in range 2 - 10. Relation of height of cone section of upper metallic shield to height of spherical section of said shield is in range 2 - 5. Apparatus allows grow large-size (with diameter and length more than 100 mm) oxide crystals (LiNbO3, LiTaO3 and others) of high optical quality and excellent structure quality.

EFFECT: possibility for growing mono-crystals with improved optical properties and enhanced structure.

FIELD: chemical technology of composite materials.

SUBSTANCE: proposed method includes mixing of starting oxides at stoichiometric ratio of components, heating the mixture at rate of 30-350°C/h to temperature of 1460-1465°C and sintering at this temperature for 6.5-8.0 h. Mixing of starting oxides may be performed at application of vibrations at frequency of 50-100 Hz and amplitude of 3-5 mm. Synthesis is carried out in alundum sleeves on whose inner surfaces layer of gallium oxide is applied. Proposed method makes it possible to obtain the charge of homogeneous phase and stoichiometric composition. Yield of phase being synthesized is practically 100%.

EFFECT: enhanced efficiency.

3 cl, 3 tbl, 3 ex

FIELD: production of acoustic electronic frequency-selective units on acoustic surface waves.

SUBSTANCE: used as monocrystal with calcium gallogermanate structures in units on surface acoustic waves is monocrystal whose geometric axis is perpendicular to thermostable shear; such monocrystal is grown by Chohralsky method with seed crystal oriented in direction perpendicular to thermostable shear. Proposed monocrystal increases number of disks up to 80% fully free from growth defects-gas bubbles.

EFFECT: enhanced efficiency; possibility of obtaining growth defects-gas bubbles.

3 cl, 2 dwg, 3 ex

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 a method and apparatus for growing a single crystal of high quality

The invention relates to solid phase synthesis mixture for growing single crystals geliysoderzhaschih oxide compounds, in particular to a method of solid-phase synthesis mixture for growing single crystals entangling tantalate by Czochralski method

The invention relates to solid phase synthesis mixture for growing single crystals geliysoderzhaschih oxide compounds, and more particularly to a method of solid-phase synthesis mixture for growing single crystals entangling niobate by Czochralski method

FIELD: production of acoustic electronic frequency-selective units on acoustic surface waves.

SUBSTANCE: used as monocrystal with calcium gallogermanate structures in units on surface acoustic waves is monocrystal whose geometric axis is perpendicular to thermostable shear; such monocrystal is grown by Chohralsky method with seed crystal oriented in direction perpendicular to thermostable shear. Proposed monocrystal increases number of disks up to 80% fully free from growth defects-gas bubbles.

EFFECT: enhanced efficiency; possibility of obtaining growth defects-gas bubbles.

3 cl, 2 dwg, 3 ex

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