Method of production of lanthanum-gallic silicate monocrystals

FIELD: growing lanthanum-gallic silicate monocrystals for making devices on spatial and surface acoustic waves and various piezo-electric and piezo-resonance transducers.

SUBSTANCE: lanthanum-gallic silicate monocrystals (langasite) are grown from charge of the following composition: La3Ga5Si0.88-0.92Ge0.12-0.08O14 (5.387-5.631 wt-% SiO2; 0.404-0.606 wt-% GeO2) in growth unit CRYSTAL-3M including loading the charge into iridium crucible, melting of charge and growth of langasite crystals on preliminarily oriented seed. Use of charge at partial replacement of silicon by germanium reduces oxygen vacancies in langasite crystals improving their quality and making them suitable for manufacture of stable units working at high temperatures.

EFFECT: enhanced efficiency.

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The invention relates to the field of growing single crystals entangling silicate (langasite)used for manufacturing devices on bulk and surface acoustic waves, as well as a variety of piezoelectric and piezoresonance sensors.

A method of obtaining single crystals vintagelove silicate crystals by the Czochralski method from a mixture obtained by solid-phase synthesis of oxides of lanthanum, gallium and silicon, taken in stoichiometric ratio and subjected to heating in air to a temperature synthesis with exposure to formation of chemical compounds. The resulting mixture is loaded into a crucible, heated to the melting temperature at atmospheric pressure and raise the langasite single crystal on the pre-oriented seed crystal by the Czochralski method (A.N.Gotalskaja et al. Langasite crystal quality improvement aimed at high-Q resonators fabrication.Proc. 1995 IEEE International Frequency Control Symposium. 49 th, pp.657-666, San Franciscoo).

The mixture, obtaining in this way does not allow in the future to grow high-quality crystals crystals not containing gaseous inclusions suitable for manufacturing devices on bulk and surface acoustic waves.

The closest is a method of obtaining single crystals entangling silicate by the Czochralski method, including solid-phase synthesis mixture by mixing the oxides of lanthanum, gpm is I and silicon, while gallium oxide charge in excess relative to the stoichiometric composition in the range of 0.1 to 2.5 wt.%, subsequent heating in air to a temperature synthesis and exposure before the formation of chemical compounds, the loading of the charge in the crucible, melting and growth of pre-oriented seed (buzunov O.A. Method of growing single crystals entangling silicate. RF patent №2108417, published. 10.04.1998, bull. No. 10). The method allows to obtain single crystals entangling silicate containing no gas inclusions and is suitable for manufacturing devices on bulk and surface acoustic waves.

The disadvantage of this method is that the obtained crystals are heterogeneous in composition and contain point defects, in particular vacancy in the position of oxygen, which showed the growing langasite crystals according to the method described in (buzunov O.A. Method of growing single crystals Rantakallio silicate. RF patent №2108417, published. 10.04.1998. Bull. No. 10). It was found that of the mixture with sverdsrikhimmash gallium oxide crystals are formed of the composition of La3Ga4(Ga1,25÷1,28Si0,75÷0,72(1))O13,88÷13,86[ ]0,12÷0,14(Kuzmicheva G., Domoroschina E., V. Rybakov, A. Dubovsky, Tyunina E. "A Family of Langasite: Growth and Structure". J. Cryst. Growth. 2005. V.275. P. e.715-e719), i.e. with a high content of oxygen vacancies (value [ ] vacancy: 0,12-0,14 formula units).

The technical solution of the present invention is that when the crystal growing crystals by the Czochralski method in an atmosphere of 98%Au+2%O2including solid-phase synthesis mixture by mixing a source of chemical reagents (oxides of lanthanum (La2O3), gallium (Ga2About3), silicon (SiO2), Germany (GeO2), and their subsequent heating in air to a temperature synthesis with exposure to formation of chemical compounds, the loading of the charge in the crucible, melting and crystal growth of langasite on pre-oriented seed crystal, in the initial charge, the silicon oxide charge in the amount of 88-92% from stoichiometry (5,387-5,631 wt.% SiO2and impose additional 8-12% of the oxide of germanium (0,404-0,606% wt. GeO2with the aim of obtaining a more homogeneous crystals containing the minimum number of oxygen vacancies. In the case of adding to the mixture of SiO2and GeO2more or less than the specified number of observed education neodnorodnogo sample.

Example.

As a source of chemicals are the oxides of lanthanum (La2About3grade Lao-D - 47,1717 wt.%, gallium (Ga2About3) qualifications OFS 15-2 - 46,814 wt.%, silicon (SiO2)complying with GOST 9428-73 - 5,387-5,631 weight percent, and Germany (GeO2), OST 48-21-72 - 0,404-0,606 wt.%. The single crystal growth of langasite is similar is a rule to the above example. The obtained crystal from charge La3Ga5Sifor 0.9Gea 0.1O14according to x-ray analysis is part of La3Ga4(Ga1,02(1)Si0,93(2)Geof 0.05(1))O13,99[ ]of 0.01(1)(in parentheses is given the standard deviation. For example, Ga with accounting standard deviation may be in the range 1,01-1,03 formula units of the Si in the range of 0.91-0.95 and so on), i.e. the concentration of vacancies in the positions of the oxygen (value [ ] - vacancies: 0,02 formula units) is at the level of accuracy of definition.

Thus, it was found that increasing the number of oxygen vacancies in the langasite crystals leads to the decrease of specific resistance and the offset values of Ttgδ(Ttgδ- temperature maximum of the dielectric loss tangent) at a lower temperature and, as a consequence, lower temperature range of application of langasite. The crystal growth of langasite structure sity with partial substitution of silicon germanium La3Ga5Si0,88÷0,92Ge0,12÷0,08O14) leads to a decrease in the number of oxygen vacancies, i.e. to increase the quality of the crystals, making them suitable for the manufacture of stable devices in the field of higher temperatures.

A method of producing single crystals entangling silicate method COHRE is skogo, including solid-phase synthesis mixture by mixing the oxides of lanthanum, gallium and silicon, and their subsequent heating in air to a temperature synthesis and shutter speed before the formation of chemical compounds, the loading of the charge in the crucible, melting and crystal growth on the pre-oriented seed crystal, wherein the silicon oxide charge in the amount of 5,387-5,631 wt.% and in addition enter 0,404-0,606% wt. oxide Germany.



 

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