The phase transitions and dielectric properties of low temperature sintered ZnNb₂O₆-Zn₃Nb₂O₈- TiTe₃O₈ microwave ceramics

ZnNb₂O₆-Zn₃Nb₂O ₈-TiTe₃O₈ ceramics were fabricated by conventional ceramic processing. The effects of TiTe₃O₈ on the microstructures and dielectric properties of 0.7ZnNb₂O ₆-0.3Zn₃Nb₂O₈ ceramics were investigated and the chemical reaction mechanisms of the phase transition were discussed. The results show that addition of TiTe₃O₈ will reduce the sintering temperature of ceramics. It is observed that ZnTiO ₃, Zn₂TiO₄ and ZnTeO₃ phases coexist with ZnNb₂O₆ and Zn₃Nb₂O ₈ phases, which results from the decomposition and reaction between Zn₃Nb₂O₈ and TiTe₃O₈. The morphology of ceramics changes significantly with increasing amounts of TiTe₃O₈. With increasing amount of TiTe₃O ₈, the dielectric constant and the temperature coefficient of resonant frequency increase, while the Q × f value decreases. The optimized composition is 0.6(0.7ZnNb₂O₆-0.3Zn ₃Nb₂O₈)-0.4TiTe₃O₈, which can be sintered at 670 C and shows the best microwave dielectric properties with τ_f of 3 ppm/ C.