SU814968A1 - Charge for synthesis of perovskite structure compounds - Google Patents

Description

The invention relates to the technology of ceramics ceramics, in particular, to the production of complex oxides of compounds of groups II and IV with perovskite structure, intended for use in radio electronic equipment, electro-acoustics, microwave technology, nonlinear optics, etc. The compositions of the charge used in radioceramic technology are known, which consist of oxides and carbonates of elements of groups I – IV of the periodic system. For example, to obtain barium titanate, a mixture consisting of barium dioxide and carbonate, taken in a stoichiometric ratio, is used. The reaction takes place according to the following reaction BaTiO + BaCOj + The latter reaction proceeds with an insignificant heat release and it is necessary to withstand the initial mixture at IOR 1300s for several hours to carry out it. The mixture for producing alkaline earth metal titanates in process combustion is closest to the one proposed. , including the components used in the following stoichiometric molar ratio (titanium, titanium oxide, barium peroxide, barium oxide) 21. 1: (1 + X): 2: X, where О Х $ 1. However, the charge for obtaining barium titanate has an adiabatic burning temperature of 1460 ° C compared with the phase transition temperature of cubic modification of barium titanate to hexagonal, which does not have the perovskite structure Sz} Poetsvlu under current conditions, when there are significant amounts of starting materials in the process reactor components and heat removal is difficult, mainly formed by hexagonal modification of the product. It is also known that barium titanate loses oxygen when heated, therefore, to obtain an oxygen-depleted product in this stoichiometric mixture, the synthesis must be carried out either in an oxygen environment or under an inert gas (argon, helium) pressure, which increases the cost of the process i. combustion temperature and simplification of the technological process in obtaining compounds with the structure of the per se with the method of technological goren. The goal is achieved by the fact that the charge for the synthesis of compounds with the structure of perovs of the method of process combustion, including metal of group IV, its oxide and metal peroxide I t of the x-flux or group IV of a subgroup, contain the components in the following ratio mol%: metal of group IV 0.1-16.4 metal oxide IV. of group 33 , 6-49.9 Metal Oxide; Group II or Group IV of a subgroup of 0.1-49.9 Peroxide of a metal of Group II or Group VI of a subgroup of 0.1-49.9 and, to obtain a bar titanate, the components are taken in the following ratio mol.%: Titan7, 3-12.8 Titanium oxide 37.2-42.7 Barium oxide 0.1-35.0 Barium peroxide 15.0-49.9, to obtain the lead titanate, the components are taken in the following ratio, mol%: Titanium 0.1-16.4 Titanium oxide 33.6-49.9 Lead oxide 0.1-49.9 Lead peroxide 0.1-49.9 A for obtaining lead zirconate, the charge contains the components in the following ratio, mol% : Zirconium 0.1-16.4 Zirconium oxide 33.6-49.9 Swine oxide and 0.1-49.9 Lead peroxide 0.1-49, in the proposed charge for barium titanate, the adiabatic temperature is below 1460 ° C and, therefore, the formation of the product in the hexagonal phase is impossible, and the use of the initial charge with an increased relative to stoichiometry oxygen content carry out synthesis under normal conditions only in a closed volume. The mixture is prepared as follows. Metal oxides) of the I and IV groups of the ChDA grade - and powdered metal of the IV group with a dispersion of not more than 150 microns are weighed, mixed well, the mixture is placed in a crucible and compacted. The combustion reaction is initiated by a tungsten coil placed on the surface of a mixture through which current is passed until the combustion reaction starts in the process combustion mode. The brightly lit front of the burning wave moves from top to bottom at a speed of up to 5 mm / s. For the synthesis of compounds with the peroxide structure in the manner described, a number of mixtures were prepared; during the combustion process, using the OPRIR pyrometer - 17, the sample temperature was measured. For barium titanate, the temperature in the combustion wave did not exceed 1460 s, for the other two compositions it did not exceed 1800 ° C. The final product in all cases had a loose structure. For barium titanate, the density is 3-4 g / cm, for lead titanate 4-5 g / cm, for lead titanate 5-6 g / cm. For barium titanate, the resulting product has a greenish gray color, and for the other two substances it is pale gray. Table 1 shows the main electrical properties of the final product. Table 2 shows the electrophysical properties of barium titanate, measured on disk samples made from the proposed mixture. Table 1

Tetrago-Tiger i Od. T BaOg.

Metati41, 9 8,1 49,8 tanat nalna tofaza bari BaT iO

37.3 12.7 48.0

Also. Also

The same - - - - 40.8 9.2 22.9

120 0.09

7750

120 0.1

7500 120 0.05 8100

Table 3 shows the X-ray phase analysis data. The presence of small impurities (3%) as the second phase was revealed.

Table

Actual

magnitude

Parameter

parameter

Losses during ignition,%

The content of BaO,% The content of TiO,%

Molecular BaO / TiOr ratio

The content of insoluble in Not residue,%

Free content

WAO,%

ZrO,%

% 10%

 %

Dielectric loss tangent

at. 20 ° С

at

Point temperature

K10ri,

The value of dielectric constant at 20 C at the Curie point

Continued table. one

Table

The tetragonality of the product obtained is high - 1.0093 (the theoretical value is 1.01), which implies a large e value.

Claims (3)

The use of the charge allows to improve. sew electrical characteristics (primarily g. and tg) of the proposed materials. An increase of 6 allows, for example, capacitors with a larger capacitance (c), since it is, and a decrease in tan f- improves the frequency characteristics of the capacitors (expands the high-frequency region), and also reduces the parasite loss and heat release in the capacitor, which allows increase the size, and hence the capacitance of the capacitor. In addition, the invention makes it possible to abandon the foreign (Japanese) technology for the synthesis of the materials in question / because the technologists using the proposed charge are simpler, more productive, less energy-intensive, simpler in instrumentation, provide more reliable environmental protection and allow to obtain a substance in npoNS conditions. Claims. 1. UbiXTa for the synthesis of a compound (with perovskite structure by the method of technological combustion, including group IV metal, its oxide, and group H or / IV group peroxide of a secondary subgroup, characterized in that, in order to reduce the burning temperature and simplify the process , it contains components in the following ratio, mol.%: Metal IV of the group 0.1-16.4 Metal oxide IV of the group 33.6-49.9 Metal oxide Group II or 0.1-49.9 Group IV side-0, 1-49.9 of the subgroup Peroxide of a metal of group II, or alkali alkali in schia chi from hours with group IV of a secondary subgroup 0, 1-49.9 2. A mixture according to claim 1, characterized in that for producing barium tanate, the components are taken in the following ratio, mol.%: Titan7.3-12.8 Titanium oxide 37.2-42.7 Barium oxide 0.1-35.0 Barium peroxide 15.0-49.9 3. Batch according to claim 1, in accordance with claim 1, in order to obtain lead anatate, the components are leached by correlation, mol. %: Titanium 0.1-16.4 Titanium oxide 33.6-49.9 Lead oxide 0.1-49.9 Lead peroxide 0.1-49.9 4. Shchit on PL, from l and h with that that, to obtain lead conate, the components are taken by Leaduk ratios, mol. %: Zirconium. 0.1-16.4 Zirconium oxide 33.6-49.9 Lead oxide 0.1-49.9 Lead peroxide 0.1-49.9 Sources of information that are taken into account in the examination 1.Okazaki K. Ceramic technologists dielectrics, M., Mechanical Engineering, 1976, p. 22 2. Authors certificate of the USSR 54585, cl. From 01 September 23, 1974. 3.Bursian E.V. Nonlinear crystal barium titanate. M., Science, 1974, 247.