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The dielectric properties and phase compositions of two kinds of SrTiO3-PbTiO3-Bi2O3. nTiO2-system ceramics, sintered with different Sr/Pb ratio, are investigated. The result shows that the ceramics, with inhomogeneous distribution of the two different systems, will present two-phase mixed structure. It will result in the superimposing effect in dielectric property as well as the double-hump characteristic in dielectric-temperature curve. Ceramic materials with high dielectric constant, low loss and low temperature variation rate can be obtained through regulating the Sr/Pb ratio within each system and the use level between two systems, and through controlling sintering temperature and the heat preservation time.

In the electrical field of line-frequency, two maximum values of breakdown strength are observed in the Sr1−xPbxTiO3.m(Bi2O3.nTiO2 ceramics with the ambient temperature changed from 20°C to 200°C. It is illustrated by the dynamic-mechanic analysis that this phenomenon corresponds with the change of the elastic modulus of the ceramics under 180°C, at which point the second peak of electrical strength located. The first peak is induced by the phase transition of secondphase material which will generate ferro-electric relaxation when the ambient temperature goes up from 80°C to 150°C. It is demonstrated by X-ray diffraction that this second-phase material is a kind of layered bismuth oxide, with the molecular formula of Sr2Bi4Ti5O18. However, its content is very hard to be illustrated by differential thermal scanning analysis and dielectric spectrum of the ceramics. As the temperature rises above 180°C, the dielectric loss and conductivity of the ceramics increase greatly, so the thermal breakdown o...