Effects of Zr substitution on microstructure and microwave dielectric properties of Zn(Ti1-xZrx)Nb2O8 ceramics

Zn(Ti1-xZrx)Nb2O8(x=0, 0.2, 0.4, 0.5, 0.6) ceramics were prepared by conventional solid-state reaction process. The effects of Zr substitution for Ti on the phase composition, microstructure, and the microwave dielectric properties of Zn(Ti1-xZrx)Nb2O8 ceramics were investigated by using X-ray diffraction and scanning electron microscopy. The phase transition from ZnTiNb2O8 to ZnZrNb2O8 occurred at x=0.5. The grain size decreased and the distribution of grain size was more homogeneous with increasing x. While epsilon(r) and (f) decreased slightly, a great improvement in Qxf value was obtained by the promoted densification and the uniform grains. The best combination of microwave dielectric characteristics was obtained for the composition of x=0.4 and sintered at 1120 degrees C for 6h: dielectric constant epsilon(r) was 33.43, quality factor Qxf reaches 59,475GHz, and the temperature coefficient of the resonant frequency (f) was -76.54x10(-6)/degrees C.