Microwave ceramics for resonators and filters

High-permittivity ceramics make it possible to noticeably miniaturize passive microwave devices. These ceramics must fulfil the requirements of high permittivity, very low dielectric losses and an extremely low temperature dependence of permittivity to yield temperature-stable resonators. Recent progress has been made in understanding the physics of microwave ceramics, particularly the property-structure relationship, in developing new materials with higher permittivity, better temperature stability and considerably lower sintering temperature, and in making co-fired multilayer devices possible, as well as in developing new microwave devices such as oscillators, antennas and band-pass filters. (C) Current Chemistry Ltd