A method of obtaining a charge for growing single crystals of strongest and strategyit with the structure of calcium gallogermanate

 

(57) Abstract:

The invention relates to chemical technology, namely the technology of preparation furnace for growing a new class of ordered four compounds galloylated with the structure of gallogermanate calcium (Ca3Ga2Ge4ABOUT14used used in piezoelectric engineering. The essence of the invention: method of solid-phase synthesis of conducting the pre-mixing through heat treatment of the oxides of the elements included in the composition of the grown single crystal strongest or strategyit Sr3MeGa3Si2ABOUT14where Me is niobium or tantalum, taken in stoichiometric ratio, and this mixture is sintered at a temperature component of 84-85% of the temperature of synthesis of the corresponding crystals. The method allows to obtain the mixture in a compact rational (in the form of a shaped tablets) for growing high-quality single crystals of galloylated. 1 PL.

The invention relates to chemical technology, namely the technology of preparation furnace for growing a new class of ordered four compounds galloylated with the structure of gallogermanate calcium (Ca3Ga2

However, the use as a component of sintered mixture of carbonate of alkaline earth metal included in the composition of the grown crystal, requires a longer heating process for its decomposition, which, in turn, increases during the process violates the stoichiometric composition of the mixture and, consequently, reduces the yield of the final gallosilikata.

The closest in technical essence and the achieved result is a method of obtaining a charge for growing single crystals of galloylated with the structure of gallogermanate calcium (Ca3Ga2Ge4O14using the method of solid-phase synthesis, by roasting in air mixture of the initial components: carbonates, alkaline earth component and oxides of the elements included in the composition of the grown single crystal at a temperature of synthesis of the corresponding single crystal within 5-12 hours (B. C. mill, E. L. Belokoneva, T. Fukuda // New connection with the structure of Ca3Ga2Ge4O14: A3XY3/P>

The disadvantage of this method is the use as a component in the sintered mixture of carbonate of alkaline earth metal, which requires long annealing for its decomposition, which increases the time of sintering the mixture, and consequently, makes the method of preparation of the charge is economically disadvantageous. Increasing time of annealing leads to loss of the volatile component, which is reflected at the output end of the grown crystal, reducing its quality. Sintering the mixture at a temperature of synthesis leads to the melting of the charge and the interaction of the melt with the crucible walls that pollutes the charge, and, in turn, grow the crystal, and also leads to the destruction of the crucibles and the impossibility of obtaining the mixture in a rational tablet form.

The technical object of the present invention is to provide an economically advantageous method of producing the mixture in a compact rational (in the form of a shaped tablets) for growing high-quality single crystals of galloylated used used in piezoelectric engineering, namely strongest (Sr3NbGa3Si2O14and strategyit (Sr3TaGa3Si2O14).

Shown is smeshivanie source element connection, included in the formula as-grown single crystals, taken in stoichiometric ratio, heating and sintering the grown single crystal strongest or strategyit has a composition Sr3MeGa3Si2O14where IU is tantalum or niobium, as a source of a mixture of compounds of elements using the corresponding oxides previously undergone heat treatment and sintering of the mixture is carried out at a temperature of 84-85% of the temperature of synthesis of the corresponding crystals.

Comparative analysis of the proposed solutions with the prototype shows that the inventive method differs from the known fact that as the source connections use only the oxides of the elements included in the composition of galloylated Sr3MeGa3Si2O14where Me is tantalum or niobium, which before mixing subjected to heat treatment and sintering of the mixture is carried out at a temperature of 84-85% of the temperature of synthesis of the corresponding crystals.

Use in the way that only oxides avoids violation of the stoichiometry of the melt during subsequent single crystal growth by reducing the duration of the annealing mixture, which reduces ="ptx2">Conducting a thermal treatment of the initial oxide also prevents the violation of the stoichiometry of the melt and, consequently, causes the exception of cultivation substandard crystals.

Sintering the mixture at a temperature of 84-85% of the fusion temperature of the respective crystals, can prevent the melting of the charge, and hence its interaction with the walls of the crucible (p. 1-4 tables).

Sintering the mixture at a temperature below that allows you to get a charge in a compact form and at a higher temperature, it is sticking to the walls of the crucible (item 5, table 6).

Examples of specific performance.

Example No. 1.

The source of the oxides of strontium - 36,8%, niobium is 15.7%, gallium 33.3% silicon, up 14.2% is subjected to heat treatment, and then weighed in stoichiometric ratio and 245 g of the mixture are mixed in a polyethylene jar with mixer type "drunken barrel", loaded at alongby the crucible, namely in the space between its inner wall and lundevall tube installed in the Central part of the crucible. The diameter Lungolago crucible was 60 mm diameter iridium crucible from which to further grow monetary synthesis strongest (Sr3NbGa3Si2O14), namely 1180°C.

In the sintering get profiled pill burden for growing single crystals of strontium-niobium-gallium silicate (Sr3NbGa3Si2O14- strongest) with a hole along its axis. From the synthesized charge grow single crystals of strontium-niobium-gallium silicate with a diameter of 1.5 inches.

Sintering of the three sub-samples of the original mixture of oxides, weight 245 grams each, allows you to get three profiled pill burden, total weight of which gives the opportunity to apply the full amount of the iridium crucible for two sessions, which will continue to grow the single crystal.

Example # 2

The same as in example 1, but starting components take the oxides of strontium - 33,3%, tantalum 23.7%, with a gallium - 30.1% silicon - 12,9%, and sintering the mixture of oxides is carried out at a temperature of 84-85% from the synthesis temperature of strategyit (Sr3Tada3Si2O14), namely 1260°C.

As a result identical way to get quality polycrystalline mixture in tablet form for growing single crystals of strontium-tantalum-gallium silicate (Sr3Tada is hty for growing galloylated with the structure of gallogermanate calcium (Ca3Ga2Ge4O14), namely strongest and strategyit allows you to:

- to reduce the number of preliminary operations;

- get profiled tablets qualitative mixture of the required mass and size to fill the entire volume of iridium crucible when growing a single crystal;

to avoid breaking the stoichiometry of the melt, as synthesized tablets are used in full towards them in the crucible, and therefore, to obtain homogeneous single crystals for use used in piezoelectric engineering.

A method of obtaining a charge for growing single crystals of strongest and strategyit with the structure of gallogermanate calcium by the method of solid-phase synthesis, including the mixing of compounds of the elements included in the composition formula of the single crystal taken in stoichiometric ratio, heating and sintering, characterized in that as the source of a mixture of compounds using the appropriate oxides previously undergone heat treatment and sintering of the mixture is carried out at a temperature of 84-85% of the temperature of synthesis of the corresponding crystals.



 

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FIELD: Czochralski method for crystal growth from melt, in particular crystals of heat-resistant multicomponent compounds.

SUBSTANCE: single crystal lithium aluminate LiAlO2 is obtained by using Czochralski method in inductive heating equipment. Crystal growth process includes batch melting containing lithium aluminate in iridium crucible followed by single crystal drawing from melt onto oriented seed crystal in inert gas atmosphere. Beforehand prepared batch-cake obtained by compounding of aluminum oxide and lithium carbonate, wherein lithium carbonate excess is 2-4 % in respect to stoichiometric ratio, is used as raw batch. Mixture is heat treated in two steps: at temperature 700oC in the first step and at 1050oC in the second one with holding for 3 h in each step. To prevent losses of volatile batch components crystallization is carried out under excess (not less than 0.3 atm) pressure of inert gas, and at the beginning of growth process broader surface square is screened, seed crystal is grown up to diameter equal to 0.8 of crucible one, then crystal is drawn up to desired length while finished diameter is decreased up to 0.5-0.6 of crucible one. As a result reusable crystal part has form of truncated cone. Single crystal lithium aluminate produced according to present invention is useful in disc production served as substrate in epitaxial film growth, in particular gallium nitride (GaN) films.

EFFECT: coarse-grained crystals of high quality.

1 ex, 1 tbl, 1 dwg

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