Glass-free low-temperature sintering and microwave dielectric properties of CaWO4–Li2WO4 ceramics

The microwave dielectric properties of (1−x) CaWO4−xLi2WO4 ceramics prepared by the solid state reaction were investigated as a function of Li2WO4 content (0≤x≤0.14). Due to the addition of Li2WO4 phase, the sintering temperature was reduced from 1150 °C to below the LTCC temperature limits. For the ceramics sintered at 900 °C and 950 °C, with the increase of x, the Q×f values first increased and then decreased. The density and permittivity presented the same behaviour as the Q×f values. At x=0.1, the (1−x)CaWO4−xLi2WO4 ceramics sintered at 900 °C/2 h presented excellent microwave dielectric properties: εr=9.002, Q×f=11.76×104 GHz and τf=−55 ppm/°C. The ceramic was a chemically compatible with silver, which makes it a very promising candidate for LTCC application.