Microwave dielectric properties and low-temperature sintering of MgTiO3–SrTiO3 ceramics with B2O3 or CuO

The effect of B2O3 or CuO addition on the microwave dielectric properties of 0.96MgTiO3–0.036SrTiO3 (MST0.036) ceramics sintered at temperatures ranging from 1070 to 1170 °C has been investigated. Addition of B2O3 successfully reduced the sintering temperature of MST0.036 ceramics from 1270 to 1170 °C. When 2 wt% B2O3 was added to MST0.036 ceramics, sintered at 1170 °C for 2 h, the apparent density of MST0.036 ceramics significantly increased from 3.57 to 3.89 g/cm3 due to liquid phase sintering. However, increase of B2O3 contents slightly deteriorated the Qf value of MST0.036 ceramics. In the MST0.036-CuO system, secondary phase was formed by reaction between MST0.036 and CuO, so the Qf value of MST0.036 ceramics steeply decreased. The MST0.036 sample with 2 wt% of B2O3, sintered at 1170 °C for 2 h, was measured to have good microwave dielectric parameters: ɛr of 19, Qf value of 75,300 GHz (at 9 GHz) and τf of −8.9 ppm/ °C.