Unleashing the potential of Mg2SiO4-based ceramics for millimeter-wave applications: Achieving ultra-low loss with enhanced temperature stability through heterovalent ion substitution

As 5G communication technology advances into millimeter-wave frequencies, the demand rises for microwave dielectric ceramics with low dielectric constant and low dielectric loss. In this regard, Mg 2 SiO 4 emerges as one of the most promising candidates. Herein, Mg 2-x Ga x Si 1-x Al x O 4 (MGSA, x = 0∼0.03) ceramics were prepared by a solid-state reaction process employing heterovalent ion substitution strategy, achieving ultra-low loss and enhanced temperature stability of resonant frequency while maintaining low dielectric constant. The effects of the partial substitution of Ga 3+ for Mg 2+ and Al 3+ for Si 4+ in MGSA ceramics were investigated by X-ray diffraction (XRD), scanning electron microscope (SEM), Raman spectra, infrared reflectivity spectra, and combined with P–V–L bond theory analysis. XRD results revealed a solid solution formation, while SEM images highlighted microstructure variations with increasing x. Based on P–V–L theory, it was found that the dielectric constant is mainly affected by average bond ionicity A f i , while τ f is mainly affected by bond energy E . The intrinsic loss determined Qf value, which is further validated by Raman and infrared spectra. The optimal performance for millimeter-wave applications was achieved at x = 0.01: ε r  = 6.95, τ f  = −37.7 ppm/ o C, Qf  = 244,800 GHz (at 27.15 GHz).