Microwave dielectric properties of CuO-V2O5-Bi2O3-doped ZnNb2O6 ceramics with low sintering temperature

Microwave dielectric properties of low temperature sintering ZnNb2O6 ceramics doped with CuO-V2O5-Bi2O3 additions were investigated systematically. The co-doping of CuO, V2O5 and Bi2O3 can significantly lower the sintering temperature of ZnNb2O6 ceramics from 1150 to 870 degrees C. The secondary phase containing Cu, V, Bi and Zn was observed at grain boundary junctions, and the amount of secondary phase increased with increasing CuO-V2O5-Bi2O3 content. The dielectric properties at microwave frequencies (7-9 GHz) in this system exhibited a significant dependence on the relative density, content of additives and microstructure of the ceramics. The dielectric constant (epsilon(r)) of ZnNb2O6 ceramics increased from 21.95 to 24.18 with increasing CuO-V2O5-Bi2O3 additions from 1.5 to 4.0 wt%. The quality factors (Q x f) of this system decreased with increasing CuO-V2O5-Bi2O3 content and ranged from 36118 to 67100 GHz for sintered ceramics, furthermore, all Q x f values of samples with CuO-V2O5Bi2O3 additions are lower than that of un-doped ZnNb2O6 ceramics sintered at 1150 degrees C for 2 h. The temperature coefficient of resonant frequency ( f) changed from 33.16 to 25.96 ppm/degrees C with increasing CuO-V2O5-Bi2O3 from 1.5 to 4.0 wt%.