Effects of V~(5+)Substitution on the Dielectric Properties of Mg_4(SbNb_(1-x)V_x)O_9 Ceramics

The effects of V~(5+)substitution on the sintering characters,microstructure and microwave dielectric properties of Mg_4(SbNb_(1-x)V_x)O_9 ceramics were investigated.Results show that a small amount of V~(5+)substitution for Nb~(5+)can lower the sintering temperature of Mg_4(Nb_(2-x)Sb_x)O_9 dras- tically.In all composition range investigated,the sintered ceramics show single phase with corundum structure.With increasing of V~(5+)content,the dielectric constant(e)and quality factor(Q·f)increase and thereafter decrease,respectively,the temperature coefficient of resonant frequenciesτ_f decreases which is due to the strengthened B site-bond valence caused by V~(5+)substitution.The ceramics with x=0.15 sintered at 1250℃has a relative dielectric constante_r of 9.98,a quality factor Q·f value of 20248GHz(at 8GHz)and a temperature coefficient of resonant frequenciesτ_f value of -23.3×10~(-6)K~(-1).