The method of etching of single crystals of lithium tantalate
(57) Abstract:The invention relates to a method of hydrothermal etching, providing for the establishment of environmentally friendly methods of etching of single crystals of lithium tantalate, used in electronic equipment. Allows etching of large single crystals of more than 2 10 10 mm (crystals when the etching does not crack), while avoiding the need to use expensive thermally inactive materials such as platinum, iridium, allowing to reduce the cost of the process and to increase the etching rate. The essence of the method consists in the processing of single crystals of lithium tantalate under hydrothermal conditions at 150 To 300°C and a pressure not less than 50 ATM, and as a pickling solution using aqueous solutions of a mixture of one of the acids H3PO4, HNO3and one of the salts MeNO3, MeF, MeHF2where IU alkaline metal, or in aqueous solutions of one of the salts MeNO3, MeF or MeHF2or in aqueous MeOH solution of alkali and salt MeNO3. The invention relates to a method of hydrothermal etching process, providing for the establishment of environmentally friendly methods of etching tantalum single crystals the crystals of tantalum lithium  includes etching in molten potassium hydroxide at 3600,2aboutC.The disadvantage of this method is low sustainability as a couple of provide the Etchant enter the atmosphere, and not a high etching rate.Closest to the invention is a method of etching tantalum single crystals of lithium  including machining and etching in a solution based on the fluorine-containing reagent. The substrate is treated to provide the Etchant from F2up to 240aboutC.The disadvantage of this method is the low environmental friendliness, because at high temperatures a large number of provide the Etchant vapors emitted into the atmosphere.The advantage of the proposed method hydrothermal etching is that there is the possibility of etching of large single crystals of more HH mm (crystals are not dissolved during etching), and there is no need to use expensive inactive temperature-resistant materials such as platinum, iridium.The technical effect is environmentally friendly method of hydrothermal etching, allowing to increase the etching rate and the cost of the etching process.The method is implemented as follows.Samples of single crystals of the preparation of the etching solution using reagents brands of reagent-grade or analytical grade. The solutions are consistently in a separate box, diluted with 90% N3RHO4up to 25% In another 25 g of NaNO3dissolved in 50 g of N2Oh, i.e., prepare a 25% solution of NaNO3. The obtained solutions are merged and mixed at room temperature. The resulting mixture is poured into a lined Teflon autoclave batch. The autoclave is sealed and set in a resistance furnace where it is heated to 150-300aboutC at a pressure of at least 50 atmospheres. At lower settings the etching rate drops sharply. Higher settings require more complex equipment. At the end of the process, the sample is washed with distilled water and dried with filter paper. The result of etching the surface of the sample becomes transparent. The etching rate of 0.9 μm/minP R I m e R 1. The sample was filled with an aqueous solution containing 40% HNO3and 10% RbNO3, was heated to 250aboutC at a pressure of 300 atmospheres. In the matte surface has become more transparent. The etching rate equal to 0.7 μm/minP R I m m e R 2. The sample was filled with an aqueous solution containing 20% HNO3and 10% NaF, was heated to 200aboutC at a pressure of 300 atmospheres. The result is. brezec was filled with an aqueous solution containing 10% HNO3and 20% KHF2, was heated to 270aboutC at a pressure of 200 ATM. In the matte surface has become more transparent. The etching rate of 1.0 μm/minP R I m e R 4. The sample was filled with an aqueous solution containing 10% LiNO3and 20% of NaF, and was heated to 300aboutC at a pressure of 500 ATM. In the matte surface was transparent. The etching rate of 0.6 μm/minP R I m e R 5. The sample was filled with an aqueous solution containing 45% NaNO3and 10% KHF2, was heated to 200aboutC at a pressure of 350 ATM. In the matte surface has become more transparent. The etching rate of 0.9 μm/minP R I m e R 6. The sample was filled with an aqueous solution containing 40% KOH and 25% KPO3, was heated to 100aboutC at a pressure of 50 ATM. In the matte surface has become more transparent. The etching rate of 0.8 μm/minP R I m e R 7. The sample was filled with an aqueous solution containing 20% KHF2, and was heated to 280aboutC at a pressure of 150 ATM. In the matte surface has become more transparent. The etching rate of 1.0 μm/min The METHOD of ETCHING of single CRYSTALS of LITHIUM TANTALATE, on malinich conditions at 150 300oWith not less than 50 ATM, and as an etching solution using the solution of the following composition (IU - alkali metal), wt.H3PO420 60
MeF 10 60
MeHF 10 70
MeF 10 70
MeHF 10 70
MeOH 20 60
MeHF > 10
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
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: 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: 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
SUBSTANCE: invention relates to the technology of growing monocrystals using Chokhralsky method. Growth of doped crystals of lithium niobate with composition close to stoichiometric is done on an inoculating crystal from molten mixture of lithium niobate of identical composition with ratio Li/Nb equal to 0.938-0.946 and containing 9-13 mol % K2O and 0.5-2.5 mol % MgO or ZnO, in conditions of applied electric field with current density of 0.2-40 A/m2. A device is provided for realising the method, comprising a housing with a growth station and a cooling chamber, crucible 1, placed in the growth station, induction heater, top metallic heating shield 4, fitted above the crucible 1, mechanism for moving the crystal with a coupling rod, a rod with a holder 3 for the inoculating crystal 2. The device is also provided with a regulated direct current source 10 with electrodes; under the inoculating crystal 2 there is an additional load from electrically conducting material, separated from the wall of the holder by electrically insulating material. One of the electrodes is connected to the crucible 1, and the second - to the load.
EFFECT: invention allows for growing large optically homogenous crystals of lithium niobate with composition close to stoichiometric Li/Nb>0,994, additionally doped with MgO or ZnO, composition of which in the top and bottom parts of the crystal is virtually the same, without destroying the inoculating crystal.
5 cl, 2 ex, 2 dwg
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
SUBSTANCE: procedure consists in mixing powders of oxides of lanthanum, gallium and tantalate with grain of granulometric dimension in range of 1-5 mcm, in successive heating produced powder-like mixture with controlled rate to temperature of sintering and in conditioning said mixture at this temperature till sintering process is completed. Also, sintering powder-like mixture of oxides is carried out in two stages, so that at the first stage heating from ambient temperature to sintering temperature T1 in the range 1300-1350°C is performed at rate 120-125 degr/hour and conditioned at this sintering temperature during 2.5-3.0 hours with formation of intermediate compounds of LaGaO3, LaTaO4 formula; while at the second stage heating is performed from temperature of sintering T1 to temperature T2 within the range 1440-1450°C at rate 150-155 degr/hour; mixture is conditioned during 3.5-4.4 hours till completion of sintering process forming stoichiometric compound of lanthanum-gallium tantalate La3Ga5,5Ta0,5O14.
EFFECT: lowered temperature of sintering, increased service life of alundum containers for their repeated usage, simplified instrumentation for process.
2 cl, 1 tbl
SUBSTANCE: invention relates to novel chemical compounds and can be used in medicine, particularly radiology as an X-ray contrast agent during X-ray examination of various organs. The invention discloses a composite tantalate of rare-earth elements with the formula M1-xM'xTaO4, where 0.01≤x≤0.45; M and M' are elements selected from a group consisting of: yttrium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, lutetium, as a contrast agent for X-ray diagnosis. The disclosed contrast agent, which provides a high level of X-ray absorption, enables to smoothly and continuously vary the level of absorption with the same quantitative content of the agent owing to change in values of x, i.e., owing to change in the ratio of atoms the first and second elements in the crystal lattice of tantalate.
EFFECT: contrast agent broadens the possibility of reliable diagnosis of cavernous organs.
SUBSTANCE: method of forming polydomain ferroelectric monocrystals with a charged domain wall involves using a workpiece in form of plate of ferroelectric monoaxial monocrystal of the lithium niobate and lithium tantalate family, which is cut perpendicular to the polar axis, one of the surfaces of which is irradiated with ion flux to form high concentration of point radiation defects in the surface layer, which results in high electroconductivity of the layer, after which an electric field is formed in the plate, directed along the polar axis, the polarity and value of which enable formation of domains on the surface of the plate which is not exposed, and their growth deep into the plate in the polar direction up to the boundary of the layer with high conductivity, which leads formation of a charged domain wall with an irregular shape, wherein the depth of the layer is determined by the value of the energy and dose of ions, and the shape of the wall is determined by the value of the electric field formed.
EFFECT: invention enables to form a charged domain wall, having an irregular three-dimensional shape with given geometric parameters, lying at a given depth in a monocrystalline ferroelectric plate without heating the plate or cutting a workpiece for making the plate.
4 cl, 7 dwg
SUBSTANCE: electrodes in the form of a system of parallel strings are applied onto two flat-parallel faces of the crystal, which are aligned at the angle of z+36° to the polar axis, wire platinum contracts are connected to electrodes, the assembled cell is placed into a furnace and heated to temperature of phase transition - Curie temperature under action of a heterogeneous electric field, as a result of which two oppositely charged domains of equal volume are formed with a flat domain-to-domain border.
EFFECT: invention makes it possible to change from traditionally used piezoceramic elements of deformation to single-crystal bidomain elements of precise positioning on the basis of single crystals of ferroelectrics with high Curie temperature, which do not have creep and hysteresis.
2 cl, 2 dwg, 1 ex
FIELD: chemical industry; other industries; methods of polishing of the silver chloride crystals.
SUBSTANCE: the invention is pertaining to the field of manufacture of the optical elements and may be used in the infrared engineering. The method provides for the abrasive polishing of AgCl crystals with the sodium thiosulfate water solution and with the finishing washing of the treated article in 30-40 % solution of 2-methyl-2-aminopropane (СН3)3CNH2 in ethanol С2Н5ОН and the following dry final polishing. The method ensures the high-accuracy polishing of the articles made out of the silver chloride crystals and the high quality of the polished surfaces.
EFFECT: the invention ensures the high-accuracy polishing of the articles made out of the silver chloride crystals and the high quality of the polished surfaces.
FIELD: microelectronics, namely processes for preparing even-atom surfaces of semiconductors.
SUBSTANCE: method comprises steps of chemical-dynamic polishing of substrate surface in polishing etching agent containing sulfuric acid, hydrogen peroxide and water for 8 - 10 min; removing layer of natural oxide in aqueous solution of hydrochloric acid until achieving hydrophobic properties of purified surface of substrate; washing it in deionized water and drying in centrifuge. Then substrate is treated in vapor of selenium in chamber of quasi-closed volume while forming gallium selenide layer at temperature of substrate Ts = (310 -350)°C, temperature of chamber walls Tc = (230 - 250)°C, temperature of selenium Tsel = (280 - 300)°C for 3 - 10 min. After such procedure substrate is again placed in aqueous solution of hydrochloric acid in order to etch layer of gallium selenide. Invention allows produce even-atom surface of gallium arsenide at non-uniformity degree such as 3Å.
EFFECT: possibility for using substrates for constructing nano-objects with the aid of self-organization effects.
FIELD: technological processes.
SUBSTANCE: invention is related to methods of processing of massive (diameter of up to 200 mm) optic elements from zinc selenide, which are used as passive optic elements of powerful CO2-lasers and other devices that work in infrared range of wavelengths. Method includes deep polishing with classified flour of aluminium oxide and deep chemical-mechanical polishing with application of polishing member material on the basis of modified oleoresin with softening temperature of 50-80°C, chemically active component, such as nitric or chloric acid or their mixture with concentration of 0.5-5 M and lubricoolant. Polishing is performed at the pressure of 25-500 g/cm2. Method makes it possible to prepare surface of zinc selenide that meets the requirements of 3rd class of surface purity according to GOST 11141-84 with deviation from the plane of not more than interferential ring with local error of not more than 0.1 of interferential ring. Speed of material removal, at mentioned conditions of processing, makes (4-11)•10-3 g/hr•cm2.
EFFECT: preparation of surface of zinc selenide.
3 cl, 5 ex
SUBSTANCE: method includes treating the surface of crystalline silicon by electrochemical etching in hydrofluoric acid solution with concentration of 20-30% while supplying current with surface density of 750-1000 mA/cm2 for 5-30 s to obtain hydrophobic silicon or supplying current with surface density of not more than 650 mA/cm2 for 5-30 s to obtain hydrophilic silicon.
EFFECT: method enables to obtain a surface with multimodal nano- or microporosity in a single step.
SUBSTANCE: composition of polishing etching agent includes the following components: 7 volume parts of sulphuric acid (98%), 1 volume part of hydrogen peroxide (30%), 1 volume part of water, 3.5 volume parts of ethyleneglycol.
EFFECT: increase of polishing speed at specified speed of disk revolution.
2 dwg, 1 tbl