Temperature compensating ZnAl2O4–Co2TiO4 spinel-based low-permittivity microwave dielectric ceramics

TiO2, CaTiO3 and SrTiO3 were added to the 0.79ZnAl2O4–0.21Co2TiO4 (ZACT in abbreviation) system to control its temperature coefficient of resonant frequency (τf). The effects of these additions on sinterability, phase compositions and microwave dielectric properties of the ceramics synthesized by the solid-state reaction were investigated. The results show that TiO2, CaTiO3 and SrTiO3 can all reduce the densification temperature of the ZACT ceramics within the scope from 75 to 150 °C. CoTi2O5 second-phase with negative τf value appears in the TiO2 doped ZACT system, which inhibits TiO2 additionʹs function for adjusting τf value of ZACT ceramics. While, CaTiO3 and SrTiO3 can both tune effectively τf value to obtain temperature-stable materials.