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 LiA1O2 ceramics and to realise the low dielectric constants (epsilon(r) < 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 y-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 degrees C and 950 degrees C (i.e., epsilon(r)=4.48, Qf=35,540 GHz and tau(f)=-53 ppm/degrees C at 900 degrees C; Qf=38,979 GHz and rf=-55 ppm/degrees C at 950 degrees C, respectively). The material prepared was chemically compatible with silver and showed potential in applications of high-frequency LTCC microwave substrates.