Effects of Li-ion substitution on the microwave dielectric properties of low-temperature sintered ceramics with nominal composition Li2xMg2-xSiO4

摘要

The effects of the partial substitution of Li+ for Mg2+ on the microstructure and microwave dielectric properties of ceramics with nominal composition Li2xMg2-xSiO4 (0.25 = x = 1.25) were investigated. Li2xMg2-xSiO4 powders were synthesised by the traditional solid-state reaction. A fixed amount of Li2O-B2O3-Bi2O3-SiO2 (LBBS) glass was used as a sintering aid to help decrease the sintering temperature to around 900 degrees C. X-ray diffraction (XRD) patterns of the sintered specimens revealed that the phase of Li2MgSiO4 gradually replaced that of Mg2SiO4 as the major phase with increased x content in the ceramics with said nominal composition. Scanning electron microscopy (SEM) images showed that moderate Li substitution contributed to densification and uniform grains in the Li2xMg2-xSiO4 (0.25 = x = 1.25) ceramics. Additionally, microwave dielectric properties were strongly related to the substitution content and sintering temperature. The sintered sample of ceramics with nominal composition Li2xMg2-xSiO4 exhibited good microwave dielectric properties when x = 1 and sintered at 900 degrees C: epsilon(r) = 6.1, Q x f = 44,500 GHz and tau(f) = -13 ppm/degrees C. These findings indicated high potential for LTCC applications.