Sintering and compositional effects on the microwave dielectric characteristics of Mg(Ta sub(1-x)Nb sub(x)) sub(2)O sub(6) ceramics with 0.25x0.35

1,500 degree C-sintered MgTa sub(2)O sub(6) ceramic exhibits microwave dielectric characteristics of epsilon sub(r)=30.5, Q x f=56,900 GHz, and tau sub(f)=28.3 ppm/ degree C, whereas 1,400 degree C-sintered MgNb sub(2)O sub(6) ceramic exhibits microwave dielectric characteristics of epsilon sub(r)=21.7, Q x f=89,900 GHz, and tau sub(f)=-68.5 ppm/ degree C. In order to find the dielectric resonators with tau sub(f) value close to 0 ppm/ degree C, the effects of sintering condition and composition on the microwave dielectric characteristics of Mg(Ta sub(1-x)Nb sub(x)) sub(2)O sub(6) ceramics (0.25x0.35) prepared under sintering temperature of 1,300-1,450 degree C are investigated. The results show that as the sintering temperature increases from 1,300 to 1,450 degree C, the epsilon sub(r), Q x f and tau sub(f) values of Mg(Ta sub(1-x)Nb sub(x)) sub(2)O sub(6) ceramics all increase and saturate at 1,450 degree C. On the other hand, as the Nb sub(2)O sub(5) content decreases, the tau sub(f) values of Mg(Ta sub(1-x)Nb sub(x)) sub(2)O sub(6) ceramics will shift to near 0 ppm/ degree C. The optimized sintering conditions and composition to obtain the Mg(Ta sub(1-x)Nb sub(x)) sub(2)O sub(6) dielectrics with tau sub(f) close to 0 ppm/ degree C are sintering temperature of 1,450 degree C, sintering duration of 4 h, and composition of x=0.25, which exhibits the microwave dielectric characteristics of sub(r)=27.9, Q x f=33,100 GHz, and tau sub(f)=-0.7 ppm/ degree C.