Enhancement quality factor by Zr+4 substitution at B-site of ZnNiTiO4 microwave ceramics

The microwave dielectric properties of ZnNi(Ti(1−x)Zrx)O4 ceramics were examined with a view to their exploitation for mobile communication. The ZnNi(Ti(1−x)Zrx)O4 ceramics were prepared by the conventional solid-state method. Second phase ZrO2 was formed due to difficulty in fully replacing Ti4+ with the relatively large Zr4+. With 0.01 mol Zr substitution, ZnNi(Ti0.99Zr0.01)O4 ceramics sintered at 1550 °C for 2 h reached the maximum relative density of 97.38% and possessed a maximum average grain size of 22.32 μm. Dielectric constant (εr) of 17.3, quality factor (Q×f) of 35,100 GHz (at 12.2 GHz), and temperature coefficient of resonant frequency (τf) of −46 ppm/°C were obtained for ZnNi(Ti0.99Zr0.01)O4 ceramics that were sintered at 1550 °C for 2 h.