Synthesis, characterization and dielectric properties of a novel temperature stable (1−x)CoTiNb2O8−xZnNb2O6 ceramic

(1−x)CoTiNb2O8−xZnNb2O6 microwave dielectric ceramics were prepared via the conventional solid-state reaction route with the aim of reducing the τf value and improving the thermal stability. The phase composition and the microstructure were investigated using X-ray diffraction, Raman spectra, and scanning electron microscopy. A set of phase transitions which were induced by composition had been confirmed via the sequence: rutile structure→coexistence of rutile and columbite phase→columbite phase. For (1−x)CoTiNb2O8−xZnNb2O6 microwave dielectric ceramics, the addition of ZnNb2O6 content (x = 0–1) led to the decrease of εr from 62.98 to 23.94. As a result of the high Q × f of ZnNb2O6 ceramics, the increase of ZnNb2O6 content also led to the lower sintering temperatures and the higher Q × f values. The τf value was reduced from +108.04 (x = 0) to − 49.31 ppm/°C (x = 1). Among them, high density 0.5CoTiNb2O8-0.5ZnNb2O6 ceramics were obtained at 1175 °C with excellent microwave dielectric properties of εr 39.2, Q × f 40013 GHz, and τf+3.57 ppm/°C.