Temperature and frequency dependence of dielectric properties of (Ba,Sr,Mg)TiO3 ceramic capacitors

The (1-y-x)BaTiO3 - ySrTiO(3) - xMgTiO(3) (0.00 less than or equal to y less than or equal to 0.25 and 0.00 less than or equal to x less than or equal to 0.20) ceramics were fabricated by the conventional ceramic process. The dielectric properties of samples were investigated while varying the composition and sintering temperature(1200 similar to 1450 degrees C) in order to obtain the optimum condition of capacitor. Curie temperature(T-c) of high dielectric-based ceramic(BaTiO3) was shifted to near room temperature by increasing the solid solution of Sr+2, and temperature coefficient of capacitance was decreased as Mg+2 was increased. From these experiments, a suitable composition for capacitor was obtained as 0.8BaTiO(3) - 0.1SrTiO(3) - 0.1MgTiO(3), also the suitable sintering temperature was 1250 degrees C for two hours. The dielectric constant of this ceramic was higher than 1300, the dissipation factor(tan delta) was smaller than 0.03 and the variation rate of capacitance was below 3% in the temperature range between -10 and 70 degrees C.