Flat profile of permittivity vs temperature for graded Ba1-xSrxTiO3 ceramics

Graded Ba1-xSrxTiO3 (BST) ceramics, which had a continuously varying graded composition from one surface toward the other of the specimen, were examined with respect to their dielectric property. Specimens were prepared by sintering superposed layers of green compacts of BST solid solutions with different values of x. The electric relative permittivity of a single phase BST ceramic showed a peak at the Curie temperature, which shifted to lower temperatures with increasing x. On the other hand, the profile of relative permittivity vs temperature of the graded BST ceramic experienced a linear characteristic. Furthermore, its slope could be controlled by changing the volume fraction of each layer. The relative permittivity was 4000-5500 +/- 5% in the temperature range from 30 to 110 degreesC.