Microwave dielectric properties of ultra-low temperature sintered Co_1−xMg_xMoO₄ (x = 0–0.09) ceramics for 5G array antenna applications at millimeter-wave frequency

This study investigates the microwave dielectric properties of pure CoMoO4 ceramics prepared using the conventional solid-state reaction method. Sintering temperatures ranging from 600° to 720°C were employed, and the effects of partial substitution of Mg2 + on these properties, specifically the sintering temperature and microwave dielectric characteristics, were examined. X-ray diffraction patterns revealed the formation of a single solid solution of Co1-xMgxMoO4 (x = 0–0.09) with a monoclinic structure and space group C2/m. Pure CoMoO4 samples sintered at 690 oC displayed dielectric properties of εr = 8.27, Q×f = 64,000 GHz, and τf = –96 ppm/°C. The partial substitution of Co2 + with Mg2 + effectively enhanced the densification of ceramics and reduced their dielectric loss and sintering temperature, which was systematically investigated with respect to dielectric polarization, lattice energy, packing fraction, and bond valence. The Co0.95Mg0.05MoO4 ceramic sintered at 630 oC exhibited excellent dielectric properties with εr = 8.42, Q×f = 71,000 GHz, and τf = –62.27 ppm/°C, and demonstrated good chemical compatibility. Furthermore, this ceramic was employed as a substrate for a 4 × 4 dual-polarized array antenna, indicating significant potential for use in ULTCC applications, particularly in the high-frequency millimeter wave region.