Cold sintering assisted CaF2 microwave dielectric ceramics for C-band antenna applications

A cold sintering process is adopted to pre-densify CaF 2 ceramics from 85.7% at 300 MPa to 91.7% at 750 MPa. Subsequent post-annealings at 1000–1150 °C lead to further improvements in densification, where great enhancements of grain size and crystallinity are also observed from the scanning and transmission electron micrographs. Significant advances in Qf values are achieved in the post-annealed CaF 2 ceramics. The optimum Qf value (80,522 GHz) is achieved after cold sintering at 750 MPa and post-annealing at 1000 °C, which is three times higher than the conventional sintered one at 1000 °C (26,448 GHz). Moreover, the obtained low- ε r (5.9–6.5) of CaF 2 ceramics suggests broad application prospects in the high-band microwave communications. A microstrip patch antenna is fabricated using the CaF 2 ceramics as the substrate, which operates at 7.89 GHz in the C-band, with an S 11 of −13.4 dB, simulated high gain and efficiency of 6.41 dBi and −0.56 dB, respectively.