Two novel low permittivity microwave dielectric ceramics Li2TiMO5 (M = Ge, Si) with abnormally positive τf

Abstract

Two tetragonal natisite structured Li2TiMO5 (M = Ge, Si) ceramics fabricated using the conventional solid-state reaction method were investigated in terms of the thermal stability, sintering behavior and dielectric properties at radio (RF) and microwave frequency region. At the optimum sintering temperature of 1140 °C, Li2TiGeO5 (LTG) has εr ˜ 9.43, Q × f ˜ 65,300 GHz (at 14.7 GHz), and τf ˜ +24.1 ppm/°C, while Li2TiSiO5 (LTS) sintered at 1180 °C exhibits εr ˜ 9.89, Q × f ˜ 38,100 GHz (at 14.2 GHz), and τf ˜ +50.1 ppm/°C. The positive τf values of the present LTG and LTS are abnormal and extremely important for low-εr microwave dielectric ceramics, which could behave as a promising τf compensator. Moreover, the dielectric spectra of both ceramics revealed a phase transition at low-temperature, exhibiting a dielectric peak, which could account for the negative τε and positive τf in operating temperature ranges.