Sintering Characteristics and Microwave Dielectric Properties of BaTi4O9 Ceramics with CuO–TiO2 Addition

Abstract

Sintering characteristics, phase evolutions, microstructures, and microwave dielectric properties have been investigated for BaTi4O9 ceramics prepared by traditional low temperature sintering using CuO–TiO2 (CT) additions as aids. The sintering temperature of BaTi4O9 ceramics was found to evidently reduce from 1350 °C to about 1100 °C with a very small amount of 0.5 wt% CT addition. When the CT addition increased to beyond 0.5 wt%, however, it was not expected to further lower the sintering temperature. Meantime, the secondary phases of Ba4Ti13O30, BaTiO3, and TiO2 were observed in these BaTi4O9-based ceramics when the CT content was beyond 2 wt%. With the introduction of the CT addition, the permittivity (ε) had little enhancement, and the temperature coefficient of the resonant frequency (τf) was improved to near zero. The BaTi4O9 ceramics with 0.5 wt% CT additions, sintered at 1100 °C, exhibited excellent microwave dielectric properties, such as ε = 36.9, Q × f = 23100 GHz, and τf = 2.5 ppm/°C. In addition, the densification mechanism and variations of the microwave dielectric properties have also been discussed with the crystal phase and microstructure’s evolution.