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

Mg 1+ x Co 1− x SiO 4 ( 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+ x Co 1− x SiO 4 ( 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 MgCoSiO 4 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+ x Co 1− x SiO 4 ( 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).