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

Abstract

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°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°C: εr = 6.1, Q×f = 44,500GHz and τf=−13ppm/℃. These findings indicated high potential for LTCC applications.