High-performance microwave dielectric composite ceramics sintered at low temperature without sintering-aids

Abstract (1-x)Li2(Mg0.96Ni0.04)SiO4+xLiZn0.93Co0.07PO4 composite ceramics were synthesised through solid-state reaction, and their sintering kinetics, microstructure and microwave dielectric properties were investigated. The perfect disconnection model was applied to explain the variation in grain growth with different x values and sintering temperatures. X-ray diffraction, scanning electron microscopy, thermo-mechanical analysis and network analysis were used to determine the macro and micro properties of the composite ceramics. Results showed that LiZn0.93Co0.07PO4 ceramic could promote grain growth and grain boundary modification, due to the different levels of shear stress and free energy density of the Si-rich and P-rich phases. The shrinkage onset point of the composite ceramics was adjusted to achieve full densification at 900 °C. The peak microwave dielectric properties are er = 5.78, Q × f = 48,168 GHz at 16 GHz and τf = −44.7 ppm/°C when x = 0.5, sintering temperature is 900 °C and relative density is 96.1%. Therefore, mixing LiZn0.93Co0.07PO4 (pre-sintered) and Li2(Mg0.96Ni0.04)SiO4 (pre-sintered) ceramics is a feasible synthesis method for microwave dielectric materials with excellent sintering and dielectric properties.