Dielectric ceramics with boundary-layer structure for high frequency application

Boundary-layer dielectric ceramics are characterized by the peculiar structure that every constituent semiconductive grain is covered with thin insulating layer which is formed by diffusion of metal oxide and oxygen. The boundary-layer ceramics made from barium titanare exhibit excellent dielectric properties but show a dielectric dispersion near 30 MHz. New type of boundary-layer dielectrics feasible in higher frequency range made from (Ba, Sr)TiO3 solid solution system are presented. Dielectric constant and dielectric loss at 1 KHz for typical (Ba, Sr)TiO3 boundary-layer dielectrics was 104to 2 × 104 and 3% to 6%. Specific resistivity for the ceramics of 0.6 mm thickness was 1010Ω. cm at 200 V/cm. Dielectric dispersion frequency extended to GHz range.