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

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 degrees C, Li2TiGeO5 (LTG) has epsilon(r) (similar to) 9.43, Q x f (similar to) 65,300 GHz (at 14.7 GHz), and tau(f) (similar to) + 24.1 ppm/C, while Li2TiSiO5 (LTS) sintered at 1180 degrees C exhibits epsilon(r) (similar to) 9.89, Q x f(similar to) 38,100 GHz (at 14.2 GHz), and tau(f) (similar to) + 50.1 ppm/degrees C. The positive tau(f) values of the present LTG and LTS are abnormal and extremely important for low-epsilon(r) microwave dielectric ceramics, which could behave as a promising tau(f) 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 tau(epsilon) and positive tau(f) in operating temperature ranges.