Effect of LiF and LBSCA glass on the microwave dielectric properties of 0.5BaCuSi₄O₁₀–0.5BaCuSi₂O₆-based ceramics for LTCC applications

In this work, the 0.5BaCuSi₄O₁₀–0.5BaCuSi₂O₆-based ceramics were synthesized using a standard solid-phase reaction process, and the inherent relationship between crystal structure and microwave dielectric properties was thoroughly explored. The crystal structure of the 0.5BaCuSi₄O₁₀–0.5BaCuSi₂O₆ ceramic was determined by X-ray diffractometer, which confirmed the existence of two phases. Microstructure observation of the ceramics was obtained by scanning electron microscope (SEM). Excellent microwave dielectric properties with a low ԑ_r ∼6.52, a high Q × f ∼46 010 GHz, and the temperature coefficient of resonant frequency (TCF) ∼−14 ppm°C⁻¹ were obtained in the 0.5BaCuSi₄O₁₀–0.5BaCuSi₂O₆ ceramic sintered at 1060°C. By adding sintering additives LiF and Li₂O–B₂O₃–SiO₂–CaO–Al₂O₃ (LBSCA) glass, the sintering temperature was decreased from 1060°C to 870°C. Good microwave dielectric properties with a ԑ_r ∼6.59, a Q × f ∼18 820 GHz, and TCF ∼−14 ppm°C⁻¹ were achieved in the 0.5BaCuSi₄O₁₀–0.5BaCuSi₂O₆ -2 wt.% LiF, 1 wt.% LBSCA (2F1LBSCA) ceramic sintered at 870°C. The low-temperature firing ceramics could also be well co-fired with Ag with good chemical compatibility. These results indicated that the 0.5BaCuSi₄O₁₀–0.5BaCuSi₂O₆ ceramic with 2F1LBSCA additions can be utilized in low-temperature co-fired ceramics technology to produce high-frequency communication components.