Microstructure and microwave dielectric characteristics of the CaxZn1−xTiNb2O8 temperature stable ceramics

The quantitative determination and the crystal structure of CaxZn1−xTiNb2O8 ceramics were analyzed by X-ray diffraction, the microwave dielectric properties were investigated. The results showed that the CaxZn1−xTiNb2O8 ceramics contained three main phases: ZnTiNb2O8 phase Zn0.17Nb0.33Ti0.5O2 phase and CaNb2O6 phase. With the increase of Ca content, the weight fraction of secondary phase Zn0.17Nb0.33Ti0.5O2 and CaNb2O6 increased. For ZnTiNb2O8, with the substitution of Ca2+ for Zn2+, the bond valence of Ti-site increased. The variation of distortion of oxygen octahedral was irregular. For Zn0.17Nb0.33Ti0.5O2, the distortion of oxygen octahedral and the bond valence of Ti-site increased with substitution of Ca2+. The increase of Ti-site bond valence led to a harder rattling of Ti cations of the specimens. As a result, the dielectric constant (e) and the quality factor value (Qf) decreased, the temperature coefficient of resonant frequency (τ f ) moved to the positive direction. The typical values of e = 38.6, Qf = 41,338 GHz, τ f = −1.28 × 10−6/°C were obtained for CaxZn1−xTiNb2O8 (x = 0.45) specimens sintered at 1100 °C for 6 h. The high dielectric properties in microwave range drive these materials a promising application in electronics.