A new microwave dielectric ceramic for LTCC applications

A new low-sintering temperature microwave dielectric ceramic was found and investigated in the Li2O–Nb2O5–TiO2 (Li2O:Nb2O5:TiO2 = 5.7:1:14.7, by mole, abbreviated as LNT) system. This new microwave dielectric ceramic shows a relatively high permittivity (47), high Q × f values up to 17,800 GHz, and low temperature coefficients (57 ppm/°C), which were obtained via sintering at 1,125 °C. With the low-level doping of B2O3–CuO (BCu) (below 2 wt%), the sintering temperature of the LNT ceramic could be effectively reduced to 900 °C. The addition of BCu does not induce apparent degradation in the microwave properties but lowers the τf value. Typically, the 2.0 wt% BCu-doped ceramics sintered at 900 °C have better microwave dielectric properties of εr = 48.7, Q × f = 16,350 GHz, τf = 32 ppm/°C, which suggest that the ceramics could be applied in multilayer microwave devices requiring low sintering temperatures.