Sintering characteristics, microstructure and microwave dielectric properties of low-ε_r CaY₂Al₄SiO₁₂ composite ceramics

The CaY₂Al₄SiO₁₂ microwave dielectric ceramics were prepared using a solid-state reaction method. XRD analysis identified the main phase as CaY₂Al₄SiO₁₂ with a secondary phase of Ca₂Al₂SiO₇. Rietveld refinement results indicated that the content of the secondary phase decreased gradually with increasing sintering temperature. SEM analysis revealed that a small amount of the secondary phase could inhibit grain growth and increase density. The Qf value was primarily influenced by non-intrinsic factors like phase composition and bulk density, while intrinsic factors affecting Qf were analyzed through packing fraction. The τ_f value showed a close correlation with phase composition. Microwave dielectric properties of CaY₂Al₄SiO₁₂ composite ceramics sintered at 1450 °C exhibited ε_r = 8.94, Qf = 35,206 GHz, and τ_f = -39.35 ppm/°C, representing the optimal performance. The Si foundation stone garnet microwave ceramics of this type, characterized by a low dielectric constant and high-quality factor, has emerged as a promising research area.