Modulation of the Microwave Dielectric Properties of Si-Based Olivine Structured Ceramics Through the Variation of A-Site Ions

Mg_1+xCo_1−xSiO₄(x = 0–0.2) microwave dielectric ceramics were prepared via a solid-phase reaction method. X-ray diffraction (XRD) data revealed a single-phase structure for these ceramics, with no phase changes with increasing Mg content, and Mg_1+xCo_1−xSiO₄(x = 0–0.2) possessed an olivine structure. X-ray diffraction (XRD) patterns were refined via the Rietveld method to obtain crystal structure information. P–V–L bond theory was applied to analyze the crystal structure changes. Scanning electron microscopy (SEM) images highlighted a dense and uniform surface grain distribution with scarce pores. Raman spectroscopy was employed to characterize the impact of lattice vibrations on the Q×f factor. Excellent microwave dielectric properties were exhibited by the MgCoSiO₄ ceramics sintered at 1250 °C for 4 h (ε_r = 7.17, Q×f = 46120 GHz, and τ_f = −61.7 ppm/°C) and the Mg_1+xCo_1−xSiO₄(x = 0.05–0.2) ceramics sintered at 1400 °C (ε_r = 6.9, Q×f = 118575 GHz, and τ_f = −47.7 ppm/°C).