Low-dielectric-constant LiAlO2 ceramics combined with LBSCA glass for LTCC applications

This study used Li2O-B2O3-SiO2-CaO-Al2O3 (LBSCA) glass to reduce the sintering temperature of LiAlO2 ceramics and to realise the low dielectric constants (ɛr<5) of low-temperature co-fired ceramic (LTCC) materials. LBSCA glass remarkably enhanced the densification of LiAlO2 ceramics. X-ray diffraction patterns indicated that only the γ-LiAlO2 phase occurred within the doping range of 1 wt% to 3.5 wt%. Scanning electron microscopy images showed dense and uniform grains in samples with 3.0 wt% LBSCA glass. These samples also exhibited low dielectric constants and low dielectric loss when sintered at 900 °C and 950 °C (i.e., ɛr=4.48, Qf=35,540 GHz and τf=−53 ppm/°C at 900 °C; ɛr=4.50, Qf=38,979 GHz and τf=−55 ppm/°C at 950 °C, respectively). The material prepared was chemically compatible with silver and showed potential in applications of high-frequency LTCC microwave substrates.