Microwave ceramics with low dielectric constant (ε_r<15), high quality factor (Q×f > 50,000 GHz) and near-zero temperature coefficient of resonance frequency (|τ_f|≤10 ppm/^oC) are drawing tremendous attentions for basic study and 5G communication. To obtain above parameters, the (1-x)Li₄Mg₂SbO₆F–xLi₂SnO₃ (x=0.65-0.85) composite ceramics were fabricated through a solid state reaction route at 825-900 ^oC. X-ray diffraction analysis showed two phase coexistence of cubic structural Li₄Mg₂SbO₆F and monoclinic structural Li₂SnO₃. The microwave dielectric properties (MDPs) of Li₄Mg₂SbO₆F-host counterpart is significantly improved with an amount of Li₂SnO₃ addition (x=0.75). For the x=0.75 composition, with increment of sintering temperature, its volume density and dielectric constant (ε_r) rose little by little, its quality factor (Q×f) rose first and then decreased, and its temperature coefficient of resonance frequency (τ_f) remained stable. Optimum MDPs with a ε_r of 12.9, Q×f of 60, 100 GHz and τ_f of -10.6 ppm/^oC were achieved at x=0.75 composition sintered at 875 ^oC, this ceramics also exhibited good co-firing chemical compatibility with silver electrode.

Keywords: Diphase ceramics, Li₄Mg₂SbO₆F oxyfluorides, Near-zero temperature coefficient.

This work was funded by grants from National Natural Science Foundation of China (No. 52272122, No. 52002317), Service Local Special Plan Project of Shaanxi Province Education Department (No. 24JC082), Xi’an Sciences Plan Project (No. 24GXFW0084, No. 25GXKJRC00053), Undergraduate Innovation and Entrepreneurship Training Program in Shaanxi Province (No. S202511664075).