Microstructure and microwave dielectric characteristics of (Zn^sub 1-x^Co^sub x^)ZrNb^sub 2^O^sub 8^ ceramics

The (Zn^sub 1-x^Co^sub x^)ZrNb^sub 2^O^sub 8^ (x = 0.1, 0.2, 0.3, 0.4) ceramics were synthesized by the conventional solid-state reaction route and sintered in the temperature range of 1160-1320 °C. The microstructure and microwave dielectric properties were investigated systematically. The X-ray diffraction results showed that the (Zn^sub 1-x^Co^sub x^)ZrNb^sub 2^O^sub 8^ ceramics exhibited a single monoclinic structure. The variation trend of dielectric constant ([straight epsilon] ^sub r^) was in accordance with variation trend of relative density. The Qf value decreased with the decrease of the packing fraction. The temperature coefficient of resonant frequency (τ^sub f^) moved towards positive due to the increase of B-site bond valence. In conclusion, the excellent microwave dielectric properties were obtained for Zn^sub 0.9^Co^sub 0.1^ZrNb^sub 2^O^sub 8^ ceramics sintered at 1240 °C for 4 h: [straight epsilon] ^sub r^ = 27.93, Q × f = 68,615 GHz (where f = 6.95 GHz), and τ^sub f^ = -61.94 × 10^sup -6^/°C.