RU2019584C1 - METHOD OF GROWING OF GALLIUM BORATE GaBO3 MONOCRYSTALS - Google Patents

Abstract

FIELD: chemical technology. SUBSTANCE: solution-melt containing GaBO₃, Ga₂O₃, PbO-B₂O₃ is overheated up to 950-1000 C at stirring, cooled up to 815-845 C, kept for 22-24 h at stirring. Then temperature is increased up to 820-850 C following by decreasing by law PbF₂ up to 810-840 C, where t-1 is time, hours. Components are taken at the following ratio, wt.-%: (10^-7-10^-8)t³ 16.8-18.6; Ga₂O₃ 42.4-42.9; PbO 27.3-28.2; B₂O₃ 11.7-12.1. Product is used in controlled solution-melting crystallization at PbF₂ preparing for physical experiment and optoelectronics. EFFECT: improved method of crystal growing. 1 tbl

Description

The invention relates to the field of controlled solution-melt crystallization and may find application in the preparation of GaBO ₃ crystals in a physical experiment and optoelectronics.

The only known method for producing single crystals of GaBO ₃ Fe ³⁺ using a borate-bismuth solvent B ₂ O ₃ - Bi ₂ O ₃ . In this method, a mixture of Ga ₂ O ₃ 5.9 g, Fe ₂ O ₃ 0.13 g, B ₂ O ₃ 6.9 g, Bi ₂ O ₃ 17.1 g was melted into a platinum crucible with a volume of 18 cm ³ . The crucible was covered with a lid and placed in an electric resistance furnace. The furnace temperature was raised to 1150 ^C and maintained for 8 hours. This was followed by rapid cooling to 800 ^{° C} with exposure 1 hour at this temperature, whereupon the temperature was rapidly raised to 880 ^{° C,} followed by a decrease to 750 ^{° C} at 2 ° ^C / hours

This method is a prototype of the invention. The disadvantage of this method is that the composition of the charge and the crystallization intervals are not quantitatively substantiated, since they are not supported by physicochemical studies and, as a result of this, the small sizes (2x2x0.5 mm ³ ) of single crystals. In addition, the use of the solvent B ₂ O ₃ - Bi ₂ O ₃ when growing GaBO ₃ crystals creates an extensive area for the liquidation of the melt solution, which makes it impossible to carry out controlled synthesis of single crystals of this compound.

The purpose of the invention is the increase in the size of single crystals and the simplification of the method of growing. This goal is achieved by the fact that PbO-PbF ₂ is introduced into the melt containing Ga ₂ O ₃ and B ₂ O ₃ in the following ratio of components, wt. %: Ga ₂ O ₃ 16.8-18.6 B ₂ O ₃ 42.4-42.9 PbO 27.3-28.2 PbF ₂ 11.7-12.1 overheating leads to 950-1000 ^о С by stirring the melt solution, then it is cooled to a temperature of 815-845 ^о С and incubated for 22-24 hours with stirring of the melt solution, then the temperature is raised to 820-850 ^о С, followed by lowering to a temperature of 810-840 ^о С according to the law (10 ^{- 7} -10 ^-8 ) t ³ , where t ³ is the time, in hours, after which the stirrer with the crystals grown on it is raised above the crucible. The crystals are separated from the stirrer.

 Comparison of the proposed method with other technical solutions in this technical field does not allow us to identify the signs proposed as distinctive, on the basis of which it follows that the claimed technical solution meets the criteria of the invention "significant differences".

The proposed method of growing uses the temperature and the ratio of the components of the solution-melt, selected on the basis of the study of the solubility curve of GaBO ₃ in a solvent of 47.7 V ₂ O ₃ ; 36.6 PbO; 15.7 PbF ₂ . The proposed compositions fit into this solubility curve. Note that the choice of such a solvent composition ensures the homogeneity of the solution-melt.

The melt solution is overheated for tper. 5-7 hours at temperatures T _per. 1000-950 ^о С with its stirring, which is 150 ^о С higher than the saturation temperature Т _us. established from physico-chemical studies. This mode ensures the transition of the solution-melt into a homogeneous state.

The temperature T ₁ 845-815 ^о С and the exposure time t ₁ 22-24 h are selected on the basis of a study of the number of crystallization centers falling on the mixer depending on the supercooling of the melt solution. The choice of such temperatures and the exposure time is sufficient to create 10-20 crystallization centers.

Then the temperature is increased by 5-7 ^about C to T ₂ . It is found that when the temperature rise of 5-7 ° C above ^the T ₁ no further occurrence of nucleation, but the melt solution is in the metastable state, which ensures slow sustained growth of the crystal.

2πρNV $\genfrac{}{}{0ex}{}{\text{2}}{\text{(}}$ _III)V_[III], где m - тангенс угла наклона кривой растворимости, равный 11,43 ˙10²; Со - концентрация GaBo₃ в растворителе в нулевой момент времени, равная 0,2425; Go - исходная масса раствора-расплава, равная 300-400 г; N - число центров кристаллизации на мешалке ≈10-20, ρ - плотность кристалла 5 г/см³, V_(III) - скорость роста кристалла и плоскости (III), равная ≈6˙ 10^-4 см/ч, V_[III] - скорость роста кристалла в направлении [III], равная ≈3˙ 10^-4 см/ч при переохлаждении ≈10^оС в динамическом режиме. Значения таких параметров дают коэффициент α≈10^-7 - 10^-8. Все эти параметры предварительно исследованы авторами.Subsequently, the temperature is lowered according to the law ≈t ³ , where t is time. For the proposed technical solution, this law is reduced by the authors to the form T _t = T ₂ - α t ³ , where Tt is the current temperature, t is time, in hours, α is a coefficient calculated from the specific conditions of the experiment and for this case, under the assumption that the crystal is approximated by a disk is

2πρNV $\genfrac{}{}{0ex}{}{\text{2}}{\text{(}}$ _III) V _[III] , where m is the slope of the solubility curve equal to 11.43 ˙ 10 ² ; Co is the concentration of GaBo ₃ in the solvent at time zero, equal to 0.2425; Go is the initial mass of the melt solution, equal to 300-400 g; N is the number of crystallization centers on the stirrer ≈10-20, ρ is the crystal density of 5 g / cm ³ , V _(III) is the crystal and plane (III) growth rate equal to ≈6˙ 10 ^-4 cm / h, V _{[III ]} is the crystal growth rate in the [III] direction, equal to ≈3˙ 10 ^-4 cm / h under supercooling ≈10 ^о С in the dynamic mode. The values of such parameters give a coefficient α≈10 ^-7 - 10 ^-8 . All these parameters were previously investigated by the authors.

T ₂ The temperature was lowered to 9-10 840-810 ^C, which is sufficient to obtain a crystal size of 15-20 2h2h1 5h5h2,5 to ³ mm. After that, raise the stirrer with the crystals grown on it above the melt solution and turn off the furnace. The crystals are separated from the stirrer in a hot 20% aqueous solution of HNO ₃ .

Temperature rise up to T _lane = 1000-950 ^{° C,} lowering the temperature to T ₁ = 845-815, the temperature rise up to T ₂ ^of 850-820 C may be conducted at an arbitrary speed, and in this case its speed is limited by the thermal characteristics of the furnace.

Thus, a reasonable choice of the composition of the mixture and the temperature regime, using data on the solubility curve, the number of centers and growth rates of crystal faces depending on supercooling, makes it possible to obtain single crystals up to 5x5x2.5 mm ³ .

The simplification of the method, compared with the prototype, consists in the fact that the temperature range of crystallization is reduced, the temperature T _per .

PRI me R 1. The mixture weighing 300 g (Ga ₂ O ₃ - 17.6 wt.% Qualification OSH, In ₂ About ₃ - 42.7 wt.% Qualification OSH, PbO - 27.8 wt.% Qualification TSP, PbF ₂ 11.9 wt.% TSP qualification) was melted into a platinum crucible with a volume of 225 cm ³ (cup cone platinum PL 99.9 TKA 07073 TU-48-1-447-83, D = 70; d = 60; δ = = 1.0; N = 70) at 850 ° ^C. The depth-directional solution melt of 25 mm. Saturation temperature T _us. = 845 ^about C.

After the charge was fused, the crucible was installed in an electric resistance furnace. The temperature in the furnace for 1-1.5 hours was raised to T _per. 1000 ^about C and withstood t _per. 5 hours with stirring of the melt solution (stirrer rotation speed ω = 60 rpm, platinum stirrer, PL 99.9 platinum). Then the stirrer was turned off, and lowers the temperature for 20-25 min to T ₁₈₃₀ ^{° C,} followed by aging for ₁ to 24 hours t and stirring the molten solution, ω = 60 rev / min. Then the temperature was raised to T ₂ 835 ^about With 1-2 minutes, followed by a decrease in the law T _t = T ₂ - 10 ^-7 t ³ . At a temperature Т _tcon ≈ 825 ^о С, the mixer, with the crystals grown on it, was raised above the crucible, and the furnace was switched off.

15–20 GaBO ₃ single crystals were obtained with sizes ranging from 2 × ₂ × 1 to 5 × ₅ × 2.5 mm ³ .

PRI me R 2. The mixture weighing 300 g (Ga ₂ O ₃ - 18.6 wt.% Qualification OSH, In ₂ About ₃ - 42.4 wt.% Qualification OSH, PbO - 27.3 wt.% Qualification TSP, PbF ₂ - 11.7 wt.% TSP qualification) was melted into a 225 cm ³ platinum crucible (conical beaker, PL 99.9 TKA 07073 TU-48-1-447-83, D 70, d 60, δ1 platinum , 0, 70) at a temperature of ≈850 ^о С. The depth of the deposited melt solution is 25 mm. Saturation temperature T _us. 860 ^C. After the batch fusing the crucible was set in a furnace of the electric resistance. The temperature in the furnace for 1-1.5 hours was raised to T _per. = 1000 ^about C and withstood t _per. 7 hours with stirring of the melt solution (stirrer rotation speed ω 50 rpm, platinum stirrer, PL 99.9 platinum). Then the mixer was turned off and the temperature decreased for 20–25 min to Т ₁ 845 ^о С, followed by exposure for t ₁ 22 h and stirring of the melt solution, ω 50 r / min. The temperature was then raised to T ₂ ⁸⁵⁰ C for 1-3 minutes followed by lowering the law T _t = T ₂ - 10 ^-7 t ^3. At a temperature T _tcon. ≈841 ^о С the stirrer, with crystals grown on it, was raised above the crucible, and the furnace was turned off. About 20 GaBO ₃ single crystals were obtained with sizes ranging from 2 × ₂ × 1 to 5 × ⁴ × 2.5 mm ³ .

PRI me R 3. The mixture weighing 400 g (Ga ₂ O ₃ - 16.8 wt.% Qualification TSP, In ₂ About ₃ - 42.9 wt.% Qualification TSP, PbO + 28.2 wt.% Qualification TSP, PBF ₂ - 12.1 wt.% TSP qualification) was melted into a 225 cm ³ platinum crucible (conical beaker, PL 99.9 TKA 07073 TU-48-1-447-83 platinum, D = 70, d = 60, δ = 1.0, Н = 70) at a temperature of ≈850 ^о С. The depth of the deposited melt solution is 15 mm. Saturation temperature T _us. 830 ^C. After the batch fusing the crucible was set in a furnace of the electric resistance. The temperature in the furnace for 1-1.5 hours was raised to T _per. 950 ^about C and kept t _per. 7 hours with stirring the melt solution (stirrer rotation speed ω = 60 rpm, platinum stirrer, PL 99.9 platinum). Then the mixer was turned off and the temperature was reduced in 20–25 min to Т ₁ 815 ^о С, followed by exposure for t ₁ 24 h and stirring of the melt solution, ω = 60 r / min. The temperature was then raised to T ₂ 822 ^C for 1-2 minutes followed by lowering the law T _t = = T ₂ - 7˙ 10 ^{-8 t} _3. At a temperature Т _tcon ≈813 ^о С, the mixer, with the crystals grown on it, was raised above the crucible, and the furnace was switched off. About 20 GaBO ₃ single crystals were obtained, sizes from 2 × 2 × ¹ to 4 × ⁴ × ² mm ³ .

 Data for other experiments shown in the same way, but with a different ratio of the components of the solution-melt, are given in the table.

Claims (1)

METHOD FOR GROWING GALLIUM BORATE SINGLE CRYSTALS GaBO ₃ , including overheating of a melt solution in a crucible containing gallium oxide Ga ₂ O ₃ and boron oxide B ₂ O ₃ , crystallization and subsequent cooling, characterized in that, in order to increase the size of single crystals and simplify the method, lead oxide and fluoride are additionally introduced into the melt solution in the following ratio of components, wt.%:
Gallium oxide Ga ₂ O ₃ 16.8 - 18.6
Boron oxide B ₂ O ₃ 42.4 - 42.9
Lead oxide RvO 27.3 - 28.2
Lead fluoride PbF 11.7 - 12.1
overheating is carried out to 950 - 1000 ^o С while stirring the melt solution with a stirrer, then it is cooled to T ₁ = 815 - 845 ^o С and incubated for 22 - 24 hours, after which the melt solution is heated to T ₂ = 820 - 850 ^o С, and then cooled at 10 ^o With the law
T _t = T ₂ - α t ³ ,
where T _t is the current temperature, ^o C;
α = 10 ^-7 - 10 ^-8 ;
t is the current time,
after which the mixer with the grown crystals is raised above the crucible and the crystals are separated.

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