Effects of B2O3 additive on ultra-low-loss Mg4Ta2O9 microwave dielectric ceramics

Abstract

The effects of B2O3 additive on the phase composition and microwave dielectric properties of Mg4Ta2O9 ceramic were investigated by solid state reaction method. The results showed that the B2O3 additive can lower sintering temperatures of Mg4Ta2O9 ceramics from 1425 °C to below 1325 °C. The XRD patterns exhibited that chemical reactions happened between Mg4Ta2O9 and B2O3 forming two new phases MgTa2O6 and Mg5TaO3 (BO3)3 during sintering in the materials. As B2O3 additive increased from 0 to 5 wt%, MgTa2O6 and Mg5TaO3 (BO3)3 phases also gradually increased. At the same time, the relative permittivity (er) increased from 11.67 to 12.57, whereas the quality factor (Qf) decreased from 280,000 GHz to 170,000 GHz, and the temperature coefficient of resonant frequency (τf) remained unchanged. The changes of the dielectric properties with the B2O3 additive content were correlated with the phase evolutions of the material during sintering. Typically, the Mg4Ta2O9-1 wt% B2O3 ceramic sintered at 1325 °C for 4 h acquired the best dielectric properties: er = 12.15,Qf = 260000 GHz,and τf = − 64 ppm/°C.