Low temperature sintering and microwave dielectric properties of CoTiNb2O8 ceramics with CuO addition

Low-fired CuO-doped CoTiNb2O8 microwave dielectric ceramics were synthesized via a conventional solid-state reaction method and the effects of CuO additives on their sintering behavior, phase composition, microstructure and microwave dielectric properties were investigated systematically. The addition of CuO to CoTiNb2O8 successfully lowered the sintering temperature from 1250 to 950 °C. Liquid phase CuNb2O6 was formed due to the chemical reaction between CuO and matrix for the CuO-containing samples; meanwhile, (Co, Cu)TiNb2O8 solid solution was detected by XRD and EDS analysis. Both of them promoted the densification of CoTiNb2O8 ceramics. The addition of CuO did not induce apparent degradation in microwave properties but tailored the τf values toward zero direction. With 2 wt% CuO, CoTiNb2O8 ceramics sintered at 950 °C reached the maximum relative density of 98.21% and possessed optimum microwave dielectric properties with εr of 61.45, a high Q×f of 15,938 GHz, and a τf of 42.12 ppm/°C, making them a promising candidate for LTCC applications.