Phase stabilization strategy for robust high Q×f values in MgSiO3-based ceramics for millimeter-wave applications

Abstract

MgSiO₃ ceramics hold promise for millimeter-wave applications owing to their low relative permittivity and cost-effectiveness, but their performance is limited by polymorphism and phase transitions. To mitigate these challenges, we strategically introduced Ge⁴⁺ ions to stabilize the orthoenstatite (OEN) phase and prepared MgSi_1-xGe_xO₃ ceramics via a solid-state method. X-ray diffraction (XRD) and Raman spectroscopy confirmed a phase transition from clinoenstatite (CEN) to OEN with increasing Ge⁴⁺ concentration, resulting in a predominantly OEN phase at x ≥ 0.15. Scanning Electron Microscopy (SEM) revealed that Ge⁴⁺ influenced grain size, uniformity and density. The relative permittivity ε_r increased from 6.07 ± 0.11–7.10 ± 0.09 with increasing x, while the temperature coefficient τ_f decreased monotonically. Optimal Q×f values of 140,000 ± 11,000 GHz at 13.1 GHz and 216,880 ± 12,840 GHz at 24.4 GHz were achieved at x = 0.15. After one year, the microwave dielectric properties remained robust, underscoring the potential of MgSiO₃ for practical millimeter-wave applications.