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, Mg2SiO4 emerges as one of the most promising candidates. Herein, Mg2-xGaxSi1-xAlxO4 (MGSA, x = 0 similar to 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 Ga3+ for Mg2+ and Al3+ for Si4+ 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 Af(i), while tau(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: epsilon(r) = 6.95, tau(f) = -37.7 ppm/C-o, Qf = 244,800 GHz (at 27.15 GHz).