Effect of lithium-based glass addition on the microwave dielectric properties of Ca[(Li1/3Nb2/3)1−xTix]O3−δ ceramics for LTCC applications

The Ca[(Li1/3Nb2/3)1−xTix]O3−δ (x = 0.2 and 0.25) (CLNT) ceramics with lithium borosilicate (LBS) and lithium magnesium zinc borosilicate (LMZBS) glasses were prepared by conventional solid state ceramic route. The effect of glass addition on the densification, microstructure and microwave dielectric properties of the CLNT ceramics was investigated. The addition of LBS and LMZBS glasses improved the densification and lowered the sintering temperature of CLNT ceramics from 1175 °C to 950 °C and 900 °C, respectively. The Ca[(Li1/3Nb2/3)0.8Ti0.2]O3−δ ceramics with 5 wt% of LBS glass sintered at 950 °C has ɛr = 30.5, Quf = 14,700 GHz (f = 4.6 GHz) and τf = −18 ppm/°C. Addition of 12 wt% of LMZBS glass in Ca[(Li1/3Nb2/3)0.8Ti0.2]O3−δ ceramics sintered at 900 °C showed ɛr = 26.2, Quf = 13,000 GHz (f = 4.8 GHz) and τf = −21 ppm/°C. The τf value decreased to below 10 ppm/°C by increasing the titanium content in the Ca[(Li1/3Nb2/3)0.8Ti0.2]O3−δ ceramics. The Ca[(Li1/3Nb2/3)0.75Ti0.25]O3−δ ceramics with 5 wt% of LBS and sintered at 950 °C/4 h has ɛr = 32.8, Quf = 11,500 GHz (f = 4.5 GHz) and τf = −2 ppm/°C. The 12 wt% LMZBS glass added Ca[(Li1/3Nb2/3)0.75Ti0.25]O3−δ ceramics sintered at 920 °C/4 h has ɛr = 28.52, Quf = 11,000 GHz (f = 4.8 GHz) and τf = −3 ppm/°C.