Method of single crystals linbo3 production and device for its implementation

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

 

The invention relates to techniques for obtaining single-crystal LiNbO3the stoichiometry and other similar compounds and their solid solutions and can find application in various industries associated with the use of nonlinear optics.

The most common method of obtaining single-crystal LiNbO3- pulling from the melt by Choralschola. The resulting crystals correspond approximately to the composition close to the composition nonvariant point (Li2O)0,52(Nb2O5)of 0.48(NVIDIA and other lithium niobate. Moscow, Nauka, 2003, str, RES).

A device for implementing this method includes the induction heater, the crucible, the mechanism for pulling the single crystal.

Solid phase LiNbO3equilibrium with the eutectic composition (Li2O)for 0.6(Nb2O5)for 0.4at a temperature of 1160°and liquidus temperature of 1250°C. Therefore, the closest analogue to obtain single-crystal LiNbO3the stoichiometric composition is extrusion of the liquid phase with a solid-phase feeding polycrystalline compound (Galazov A.A. ABOUT obtaining a solid solution semiconductor compounds. "Izv. THE USSR ACADEMY OF SCIENCES. Inorganic materials. t, No. 4, 1983, str, last paragraph).

A device for implementing this method consists of a heater, fur the ISM pulling, the crucible and the lattice, which is fueling the solid phase (Ajanensis. Technology of semiconductor materials. M, metallurgy, 1972, str, risb).

The disadvantage of this method is the low quality of the crystals, in the form of druses, due to the effect of the concentration of hypothermia, as well as inclusions of particles of the solid phase, a pop-up when dissolved recharge for semiconductors or air bubbles to oxides.

The disadvantage of this device is the lack of implementation of solid-phase feed mixture sintered oxide of stoichiometric composition due to the small interval between the liquidus temperature and the solidus, as well as low thermal conductivity of the ingot, leading to the occurrence of temperature gradients in the hundreds of degrees per centimeter. Therefore, the ingot begins to melt from the bottom, which is unacceptable, since the liquid-phase feed should be managed, and in these conditions, be as it may not.

The technical challenge is to obtain structurally perfect single-crystal LiNbO3the stoichiometric composition.

The problem is solved by a method of obtaining single-crystal LiNbO3the stoichiometric composition comprising pulling a single crystal from the liquid of eutectic composition with a solid-phase feeding pre-synthesized compound, heated the m at the bottom. Recharge the solid phase is additionally heated from above two-layer spiral heater placed in the liquid phase, and reducing the temperature gradients in the liquid phase and the single crystal is performed by using a furnace for heating the single crystal.

Unlike the prototype is that recharge the solid phase is additionally heated from above two-layer spiral heater placed in the liquid phase, and reducing the temperature gradients in the liquid phase and the single crystal is performed by using a furnace for heating the single crystal.

These differences provide a solution to the task. Heating of the feed of the solid phase from the top makes it dissolves and eliminates melting from below. The use of two-layer spiral heater eliminates the effect of the concentration of hypothermia and prevent the growth of the druses, and reducing temperature gradients in the liquid phase and the single crystal is performed by using a furnace for heating a single crystal, which further reduces the internal stress and the linear density of dislocations in the single crystal.

The device for implementing the method of obtaining single-crystal LiNbO3the stoichiometric composition includes a mechanism for pulling a single crystal, insulated the ü with a solid-phase support, flat crucible heater with insulation, which has a two-layer spiral heater with a cross-section of the spirals in the form of inverted troughs, covers all the cross-section of the crucible mounted with clearance on the recharge solid phase. The electrode double-layer spiral heater pass through the insulation of the furnace for heating the single crystal and bonded with her.

Unlike the prototype is that there is a two-layer spiral heater with a cross-section of the spirals in the form of inverted troughs, covers all the cross-section of the crucible mounted with clearance on the recharge solid phase electrodes which pass through the insulation of the furnace for heating the single crystal and bonded with her.

These differences provide a solution to a technical problem. So double-layer spiral heater with a cross-section of the spirals in the form of inverted troughs, covers all the cross-section of the crucible, removes air bubbles released during the dissolution of the recharge of the solid phase from the crystallization front to the walls of the crucible. Installing double-layer spiral heater with a gap for feeding the solid phase provides heated to a temperature of dissolution and eliminates the effect of the concentration of hypothermia, provided that reduces the value of the temperature gradients in the liquid phase and the single crystal, what is the use of the oven with insulation for heating the pulling of the single crystal contained in the crucible as the dissolution of feeding and growth of the single crystal.

The drawing shows a diagram of a device for obtaining single-crystal LiNbO3in the section.

Apparatus for producing single-crystal LiNbO3shown in the drawing, consists of a pulling mechanism with the rod 1, the crucible 2 with the heater 3 and the heat insulation 4. On bottom of the crucible 2 is fueling the solid phase 5, and above the liquid phase 6. Solid phase 5 with a gap set double-layer spiral heater 7, a spiral which have in cross section the form of inverted troughs, covers all the cross-section of the crucible 2. The electrodes 8 a two-layer spiral heater 7 is bonded with oven 9 to heat the pulling of the single crystal 10 and reduce temperature gradients in the liquid phase 6.

To obtain single-crystal LiNbO3the device is used as follows. Pre-prepare recharge solid phase 5 stoichiometric composition. On the surface recharge solid phase 5 fill a homogeneous mixture of powders (Li2O)0,55(Nb2O5)0,45, level and establish a two-layer spiral heater 7, plunging it into powder by rotation in different directions until it stops to feed on the surrounding solid phase 5. Through the furnace 9 fall asleep the second part of the mixture of powders (Li2O)for 0.6(Nb2O5)for 0.4eutectic composition, which provides the sequence of melting and the most rapid establishment of diffusive flux to the growing single crystal 10. The total number of consumable substances provides the layer thickness of the liquid phase 6 after melting 10-15 mm, separated by a two-layer spiral heater 7 in height into three equal parts. In the furnace 9 enter the single crystal 10 is mounted on the stem 1 of the mechanism of pulling the single crystal, and include all the heaters. Heater 3 set the temperature of the bottom of the crucible 1240°C. double-layer spiral heater (7) set the temperature of 1250°on the surface of the solid phase 5 and a temperature of 1100°in the lower part of the furnace 9. Temperature control thermocouples platinum group, not shown in the diagram. Put the single crystal 10 to contact with the liquid phase 6, by controlling the process based on the sensor readings of the weight of the crystal. When you reduce the weight of the single crystal 10 reduce the oven temperature 9 small steps (0.5 to 1° (C) to stabilize the weight. Install the program pulling in proportion to the increase in weight for a given diameter of the single crystal 10. The process of growth of the single crystal 10 is of a diffusive nature, and therefore, its rotation is not about swagat, and growth rate are in the range of 120-200 μm/hour. The process is carried out until it stops annular ledge insulation furnace 9 in the insulation 4 of the crucible 2, which prevents the lowering and closing the bottom of the crucible double-layer spiral heater 7. After pulling the single crystal furnace 10 and 9 dual-layer spiral heater 7 is turned off and removed from the residue of the liquid phase 6, and after melting residues recharge solid phase 5, the heater 3 is switched off and the melt is poured into a cold crucible. All parts in contact with the liquid phase, is made from platinum or platinum group metals.

Method and device for its implementation provide a structurally perfect single-crystal LiNbO3the stoichiometric composition with an accuracy of about 0.1%, with precision temperature of 0,5°C. Despite the low growth rate, its low power consumption, the method and apparatus provide more than twice the energy savings in comparison with traditional methods, using induction heating.

1. The method of obtaining single-crystal LiNbO3the stoichiometric composition comprising pulling a single crystal from the liquid phase eutectic composition with water the solid phase pre-synthesized compounds, heated from below, otlichalis the same time, that recharge the solid phase is additionally heated from above two-layer spiral heater placed in the liquid phase and installed with a gap relative to the recharge of the solid phase, thus reducing the temperature gradient in the liquid phase and the obtained single crystal by use of the furnace for heating the single crystal.

2. Apparatus for producing single-crystal LiNbO3the stoichiometric composition comprising mechanism for pulling a single crystal, insulated crucible recharge the solid phase, flat crucible heater with insulation, characterized in that it comprises a two-layer spiral heater with a cross-section of the spirals in the form of inverted troughs, covers all the cross section of the crucible is installed with a gap relative to the recharge of the solid phase, while the two-layer spiral heater is equipped with electrodes passing through the insulation of the furnace for heating the single crystal and bonded with her.



 

Same patents:

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

The invention relates to a hydrothermal process for the preparation of single crystals of solid solutions (Sb1-xBix)NbO4(x = 0.4 mol) and can be used in piezoelectric, pyroelectric field, as well as in chemical technology to create composite materials for various purposes

The invention relates to a hydrothermal process for the preparation of single crystals of solid solutions on the basis of ferroelectric compounds of orthotantalat antimony Sb(SbxTa1-x)O4(x=0.25 mol) and can be used in pyroelectric, piezoelectric region, as well as in chemical technology to create a related composite materials

FIELD: processes and equipment for growing large-size crystals with use of double crucible at adding initial material to melt.

SUBSTANCE: method comprises steps of heating growing unit at controlling temperature; adding palletized charge to crucible By means of metering device; approaching seed to surface of melt; drawing upwards rotating seed crystal and automatically controlling diameter of grown crystal due to regulating rate of making up melt level and power supplied to bottom heater. Melt level is sustained during the whole process as H ≤ [1708 x kν/gαΔТ]1/3 - h where g = 9.8 m/s2 -gravity acceleration; α -temperature coefficient of volumetric expansion; h - meniscus height of melt; ΔT- temperature difference of crucible bottom and crystallization front; k - thermal conductivity of melt k = λ/ρС where λ - heat conductivity, ρ - melt density; С - heat capacity of melt at constant pressure; ν - kinematic viscosity of melt. Apparatus for performing the method is also offered. Due to selection of melt level in the result of absence of free convection of melt and due to possibility for controlling crystallization front, it is possible to achieve axial and radial uniformity of crystal and to increase controllability and reproducibility of process. Due to selecting height of walls of outer and inner portions of crucible where R - crystal radius; μ - coefficient of heat removal from crystal surface; λ - coefficient of crystal heat conductance; and melt level on base of control of axial temperature gradient of crystallization front it is possible to improve axial uniformity of crystal.

EFFECT: enhanced quality of crystal, improved efficiency of crucible, less consumption of crucible material.

5 cl, 5 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: crystal growing.

SUBSTANCE: invention relates to technology of growing monocrystals seed crystal and can be used for growing monocrystals having different chemical composition, e.g., types A2B6 and A3B5, as well as monocrystals of refractory oxides, for instance sapphire. In a method preparing monocrystals by growing them from melt comprising melting starting material and drawing monocrystal by crystallization of melt on seed crystal at controlled removal of crystallization heat and use of independent heating sources forming own heat zones, according to invention, independent heating sources form two equal-sized coaxially disposed heat zones so that unified thermal melt and grown crystal region is created separated by melt mirror. Starting material is melted in two steps: first upper heat zone is heated by feeding upper heater with 50% power required to produce melt until maximum temperature providing stable state of seed crystal solid phase is attained, after which the rest of power is directed to lower heat zone onto lower heater at unchanged temperature of upper heat zone until batch is completely melted. Enlargement and growth of monocrystal proceed at controlled lowering of temperature in upper heat zone and preserved unchanged power fed into lower heat zone. Furthermore, crystallization heat is removed in crystal enlargement and growth step at a velocity calculated from following formula: g/sec, where Δm denotes crystal mass, g; Δτ denotes mass growth (Δm) time; Tmelt melting temperature of starting material, °C; Tcrit maximum temperature of stable state of seed crystal solid phase, °C; ΔT temperature change in upper heater in the process, °C; ΔHmelt specific melting point, cal/g; ρ pressure const; R crystal radius, cm; A = ΔT/ΔR is radial temperature gradient near crystallization zone, °C/cm; is initial axial temperature gradient in crystal growth zone, °C/cm; Cp specific heat capacity, cal/g-°C'; and λ heat conductivity of crystal, cal/cm-sec-°C.

EFFECT: achieved independence of process of grown monocrystal material, increased productivity, and increased structural perfection of monocrystal due to lack of supercooling in the course of growth.

2 cl

FIELD: crystal growing.

SUBSTANCE: crystal growing apparatus comprises double-section chamber, seed holder fixed on rod, crucible, furnace provided with heater assembled on U-shaped lamellas following the crucible outline, centering ring with closed parts of lamellas attached to it, and water-cooled annular current leads. According to invention, furnace is constructed in the form of two heaters similar in shape, mass, and size, which are mirror reflection of each other; closed parts of U-shaped lamellas are attached to centering ring being moved apart to 90°; rod with seed holder is disposed inside upper heater; free ends of lamellas are connected through conducting adapters to current leads with alternation of current charge signs as follows: "++--"; crucible is supported by insulated supports disposed between heater lamellas; conducting adapters are made from refractory material having resistivity lower than that of lamellas; and ends of adapters connected with lamellas are positioned at the same distance from axis of heater.

EFFECT: enabled growing large-size monocrystals and increased their structural perfection due to lack of supercooling of melt and increased service time of units.

6 cl, 2 dwg

The invention relates to the technology of silicon for the semiconductor industry by Czochralski method

The invention relates to the field of obtaining single crystals of semiconductor materials and can be used for growing silicon single crystal from a melt by the Czochralski

The invention relates to the production of single crystals, to a device for growing single crystals from the melt, and can be used to obtain calibrated profiled bulk single crystals, in particular sapphire

The invention relates to the technology of growing single crystals from a viscous melt refractory oxides by Czochralski method for producing three-dimensional shaped single crystals with a high degree of perfection patterns

The invention relates to the cultivation of molten sapphire crystal and is aimed at improving the thermal protection system

The invention relates to the production of single crystals and can be used in the technology of growing single crystals from a viscous melt refractory oxides by Stepanov method for obtaining three-dimensional profiled calibrated single crystals of large diameter with a high degree of perfection patterns

FIELD: technological process.

SUBSTANCE: invention is related to the field of crystals growing and may be used in electronic, chemical industries, in jewelry-making. Method consists in melting of primary stock, seeding onto rotating primer, growing of crystal conical part and crystal pulling. As primary stock mixture of terbium and gallium oxides mixture, after conical part growing has been commenced, the speed of single crystal pulling from melt is reduced according to the following dependence vL=v0-kL, where vL - speed of pulling at crystal length L, mm/hr, v0 - speed of pulling at the beginning of crystal conical part growing, which is equal to 2-7 mm/hr, L - current value of crystal length, mm, k - proportionality constant, which is equal to 0.1-0.2, at that angle of conical part growing is at least 140°.

EFFECT: allows to prepare homogeneous crystals with minimum concentration of defects and increased output of available cylindrical part.

1 ex

Up!