Rapid densification mechanism of SrZn_0.8Mg_0.2Si₃O₈ microwave dielectric ceramics

SrZn_0.8Mg_0.2Si₃O₈ ceramics capable of rapid densification under atmospheric pressure, while maintaining excellent microwave dielectric properties were investigated. In-situ scanning electron microscopy and high-resolution transmission electron microscopy confirm the formation of a liquid phase during sintering and clarify its chemical composition. Rapid densification originates from intrinsic generation of this liquid phase in SrZn_0.8Mg_0.2Si₃O₈ during the sintering process. Because the liquid phase is produced internally, most of it spontaneously crystallizes into the parent phase during cooling. Therefore, the final microstructure consists predominantly of the SrZn_0.8Mg_0.2Si₃O₈ phase with only a small residual amorphous phase. SrZn_0.8Mg_0.2Si₃O₈ ceramics thus exhibit excellent microwave dielectric properties (ε_r = 6.07 ± 0.02, Q×f = 69,350 ± 650 GHz (f = 16.37 GHz), τ_f = −27.6 ± 1.4 × 10⁻⁶ ℃⁻¹, holding time(H.T.) = 1 min), which are superior to those of conventional composite ceramics that rely on added low-melting-point oxides to induce liquid-phase sintering. In addition, rapid densification enables grain refinement while maintaining high relative density. This microstructural feature improves mechanical strength and electrical breakdown strength and suppresses long range ionic diffusion during heterogeneous cofiring integration.