Enhancing Sintering Behavior and Microwave Dielectric Performance: Low-Temperature-Fired Baf2-Lif Ceramics for Ltcc and Mmwave Dielectric Resonator Antenna Applications

BaF2 is a promising fluoride with excellent microwave dielectric properties, while densification of BaF2 ceramics is challenging even at high sintering temperatures above 1000°C. In this work, the addition of LiF could efficiently boost the densification of BaF2–xwt%LiF (x = 0, 0.10, 0.25, 0.50, 1.00) ceramics from 90.8% to 97.3% and simultaneously reducing the sintering temperature from 1025°C to 700°C. Excellent microwave dielectric properties with εr = 7.34, Qf = 64,442 GHz, and τf = –67.2 ppm/°C were achieved at x = 0.25, where the Qf value was 1.2 times higher than that of pure BaF2 ceramics (53,654 GHz). Additionally, the favorable chemical compatibility with Ag powders indicates the promising potential of BaF2–xwt%LiF ceramics for Low-Temperature Co-Fired Ceramic (LTCC) applications. Furthermore, a millimeter-wave antenna working at 26.34 GHz was fabricated using BaF2–0.25wt%LiF ceramics as the dielectric resonator, which demonstrated exceptional performance with a S11 value of –46.6 dB and a large bandwidth of 2.7 GHz.