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.