Sintering and compositional effects on the microwave dielectric characteristics of Mg(Ta1-xNbx)2O6 ceramics with 0.25 ≤x≤0.35

1,500 °C−sintered MgTa2O6 ceramic exhibits microwave dielectric characteristics of ɛr = 30.5, Q × f = 56,900 GHz, and τf = 28.3 ppm/°C, whereas 1,400 °C-sintered MgNb2O6 ceramic exhibits microwave dielectric characteristics of ɛr = 21.7, Q × f = 89,900 GHz, and τf = −68.5 ppm/°C. In order to find the dielectric resonators with τf value close to 0 ppm/°C, the effects of sintering condition and composition on the microwave dielectric characteristics of Mg(Ta1−xNbx)2O6 ceramics (0.25 ≦ x ≦ 0.35) prepared under sintering temperature of 1,300–1,450 °C are investigated. The results show that as the sintering temperature increases from 1,300 to 1,450 °C, the ɛr, Q × f and τf values of Mg(Ta1−xNbx)2O6 ceramics all increase and saturate at 1,450 °C. On the other hand, as the Nb2O5 content decreases, the τf values of Mg(Ta1−xNbx)2O6 ceramics will shift to near 0 ppm/°C. The optimized sintering conditions and composition to obtain the Mg(Ta1−xNbx)2O6 dielectrics with τf close to 0 ppm/°C are sintering temperature of 1,450 °C, sintering duration of 4 h, and composition of x = 0.25, which exhibits the microwave dielectric characteristics of ɛr = 27.9, Q × f = 33,100 GHz, and τf = −0.7 ppm/°C.