Permittivity and temperature response of complex niobate perovskite dielectrics

Dielectric materials in the barium strontium zinc cobalt niobate system have been prepared to explore the consequences of independent variation of the population of the A and B sites in the perovskite structure. Results for the temperature coefficient of the resonant frequency follow the empirical relationship with the “t” factor established by Reaney. Permittivity results show deviation from linear behaviour with composition as previously observed by Kim. By comparing ionic polarisibilities calculated from the measured permittivities using the Clausius–Mossotti equation and from the ion additivity rule we show that the anomalous results are those for the high barium compositions. We demonstrate that these can be explained by compression of the A site ions and propose a simple calculation to estimate the extent of this effect which agrees well with the experimental results.