Phase Evolution, Microstructure and Microwave Dielectric Properties of Zn1.9-2xLixAlxSi1.05O4 Ceramics

Phase evolution, microstructure, and microwave dielectric properties of Li2O and Al2O3 doped Zn1.9Si1.05O4, i.e., Zn1.9-2xLixAlx-Si1.05O4, ceramics (x = 0.02 similar to 0.10) were investigated. The ceramics were densified by SiO2-rich liquid phase composed of the Li-AlSi-O system, indicating that doped Li and Al contributed to the formation of the liquid. As the secondary phase, beta-spodumene solid solution with the composition of LiAlSi3O8 was precipitated from the liquid during the cooling process. The dense ceramics were obtained for the specimens of x >= 0.06 showing the rapid densification above 1000 degrees C, implying that a certain amount of liquid is necessary to densify. The specimen of x = 0.06 sintered at 1050 degrees C exhibited good microwave dielectric properties; the dielectric constant and the quality factor (Q x f(0)) were 6.4 and 11,213 GHz, respectively.