SU868850A1 - Dielectric for capacitor - Google Patents

Description

The invention relates to electrical engineering, namely, dielectrics for variable capacitors, which vary with a frequency variation of an electrical voltage, which may be used, in particular, in continuous phase shifters. The rate of change in the capacitance of such capacitors with a change in the frequency of the electric voltage can be characterized by the frequency coefficient of capacitance K Eg (, j) / Eg (fi / f), where C and Cl are the capacitors measured at the electric voltage frequency f and f2 respectively. The larger the capacitance frequency coefficient of a capacitor, the faster the capacitor's capacity changes as the frequency of an electrical voltage changes. A dielectric capacitor for variable capacitors, varying with a change in the frequency of the electrical voltage, is known, consisting of a heterogeneous mixture of emulsion polystyrene and aluminum (mini powder |. It does not change the capacitor capacitance quickly enough by varying the frequency of the electrical voltage, which, in turn, prevents the use of capacitors with such a dielectric in the following phase shifters The closest to the proposed technical essence is a dielectric for a lead titanate-based capacitor, which includes the addition of a spruce element from the scandium subgroup tz. The disadvantage of this dielectric is also a small frequency coefficient of capacitance reaching 66%. This goal is achieved by the fact that the dielectric for a capacitor on new lead titanate, which includes the addition of an oxide element from the scandium subgroup, additionally contains glass at the following the ratio of components wt.%: Lead titanate, which includes the addition of an oxide of an element from the subgroup of scandi 95-99 Glass1-5. This glass contains, wt%: PHO 37-45 GeOj 38-51 12-17, and as an additive of an oxide of an element from scandi subgroups use lutetium oxide. A capacitor dielectric is obtained by mixing the initial lead titanate with the addition of lutec oxide and glass, pre-crushed to pass through a sieve of 10,000 holes. /cm. or grinding and blending operations are conducted jointly. The starting material - lead titanate with the addition of lutetium oxide - is obtained by conventional ceramic technology. The synthesis is carried out from oxides PbO, TiO, taken in the following ratio, wt%: PbO 73.35; TU 26.0; LuQQ. ,, 0.65. The synthesis temperature is 750–900 ° C, and the holding time at this temperature is 24 h. Glass is obtained by fusing oxides of PbO, GeO – ij with platinum crucible at 1150–120 ° C for 1–2 h, followed by quenching in air. To obtain a dielectric for a capacitor from mixtures of ovine titanate, an additive of lutetium with glasses is pressed into samples, for example, in the form of disks with a diameter of 12 mm and a thickness of 23 mm. Then they are burned in a chamber electric furnace at 1000-1050 C for 3-4 hours in the filling of the composition, wt.%: PbTiO 90; MgABi04 Yu. The temperature in the furnace is raised at a speed of 200-250 degrees / h, cooling at a speed of 80-120 degrees / h (the loss in weight of the samples does not exceed 0.5%). The resulting discs are polished to a thickness of 1 mm and electrodes are applied to the surface of the samples using the gray paste firing method. The composition of the dielectric, Example. % by weight: Pb (Tij, gg o. 95 and glass 5. Glass composition, weight: PHO 39; eOi 47;, 14. Preparation of lead titanate with a lutetium oxide, glass and dielectric for a capacitor made from them as described above technologies: synthesis temperature of lead titanate with added lutetium oxide, synthesis time 24 hours, fusing temperature of oxides to produce glass 1150s, fusing time 2 hours. Roasting temperature of samples of a mixture of lead titanate with addition of lutetium oxide glass, calcining time 4 hours for capacitors of compositions shown in Tables 1 and 2 To characterize capacitors with the proposed dielectrics, they measure their capacitance at different frequencies of electrical voltage. Measurements are carried out using a phase-sensitive voltmeter. The test results and compositions of the dielectrics used in the experiments are listed in Tables 1 and 2. glass 1-5 wt.% has a frequency coefficient capacity in the range of 93-105%. With less or more glass content, the ceramic material is poorly baked and the samples have high porosity. The frequency ratio of the capacitor capacitor of the Pb dielectric (T o is 66%, and of the Pbit 0l dielectric is 56%. As can be seen from Table 2, the following ratio of oxides in glass, wt.%: PHO 39; COL 47; 1 b; P approach to the limiting ratios of the content of oxides in glass, the frequency ratio of the capacitor's capacitance decreases. The capacitance factor is 1.5 times the frequency coefficient of the capacitance of the known, which improves the characteristics of the following phase shifters.

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Claims (2)

Ck. DETAILS OF THE INVENTION A dielectric for a lead titanate-based capacitor comprising the addition of an oxide element of the scandium subgroup, characterized in that, in order to increase the frequency capacitance coefficient, it additionally contains glass at the following ratio of components, wt.%: elements from the subgroup scandi 95-99 Glass1-5 Table 2 At the same time, glass contains, wt.%: PHO 37-45 GeOi 38-51 (-JI f., I a use lutezium oxide as an additive to the oxide of an element from the scandi subgroup. The sources of information taken into account in examination 1, USSR Author's Certificate No. 132721, cl. N OlG 7/06, 30.09.56 2. Crystallization and crystal properties. 2. Novocherkassk, 1975, p. 18 (prototype).