Effect of CuO on the sintering and cryogenic microwave characteristics of (Zr0.8Sn0.2)TiO4 ceramics

The effect of CuO on the sintering temperature, microstructure and microwave dielectric properties of (Zr0.8Sn0.2)TiO4 (ZST) modified with 1 wt% of ZnO has been investigated. Microwave dielectric properties of ZST ceramics are measured from cryogenic to room temperatures (15-290K). Crystallite sizes of sintered ZST ceramics as derived from XRD are in the 30-50nm range. The addition of CuO effectively reduced the sintering temperature to 1300 degrees C, possibly due to liquid-phase effects. Addition of CuO did not cause any secondary phases up to 1.5wt% of CuO. The dielectric constant (epsilon(r)) and temperature coefficient of resonant frequency (tau(f)) of ZST ceramics do not significantly vary with temperature, whereas the unloaded quality factor (Q(u)) changes noticeably. It is found that the Q(u) factor of the sample without CuO decreased with increase in temperature, whereas the samples with addition of CuO up to 1.0wt% showed less dependence on temperature. The Q(u) factor of CuO-free ZST is 15,000 and that of ZST with 0.5 wt% of CuO is 11,800 at 15 K. The Q(u) factor while measured at room temperature ranged between 2900 and 7000. Efforts were made to understand whether the increase in Q(u) factor at both cryogenic and room temperatures is the result of intrinsic or extrinsic factors. (c) 2007 Published by Elsevier Ltd.