Research on sintering behavior and microwave dielectric property of (Mg0.95Ca0.05)TiO3 ceramics for cross coupling filter

摘要

The microwave dielectric properties of 0.95% MgTiO3-0.05% CaTiO3 (abbreviated as 95MCT hereafter) ceramics have been studied for application in dielectric cross coupling filters. ZnO and Nb2O5 were selected as liquid sintering aids to lower the sintering temperature and enhance the Qf value of 95MCT and simultaneously we varied the mole ratio of ZnO:Nb2O5 to tune the microwave dielectric properties of 95MCT. When the ZnO:Nb2O5 mole ratio was 1.5 and the co-doping content was 0.25 wt.%, the optimal sintering temperature of 95MCT ceramic could be lowered from 1400 degrees C to 1320 degrees C and the Qf value could be improved by about 7.7%. The optimal microwave dielectric properties obtained under this condition were Qf = 72730 GHz (6.8 GHz), epsilon(r) = 20.29 and tau(f) = -6.84 ppm/degrees C, which demonstrated great potential usage in ceramic industry. High values of Qf ceramic were used to design the dielectric cross coupling filter. The dielectric filter measured at 2.35 GHz exhibited a 6.7% bandwidth (insert loss > -3 dB) of center frequency.