Low-temperature sintering and microwave dielectric properties of Ca2+ substituted Ba0.8-xCaxSr0.2CuSi2O6 ceramics

For matching formulation of Ba 0.8−x Ca x Sr 0.2 CuSi 2 O 6 (BSCS-Ca x ) (x = 0–0.1) ceramics with low-temperature co-fired ceramic materials, in this study, BSCS-Ca x ceramics were synthesized by a solid-state reaction method, Further, the sintering temperature was reduced to 925 °C by adding a small amount of LBSCA glass (0.4 wt.%) and BSCS-Ca x +0.4wt.% LBSCA (BSCS-Ca x -L) ceramics were obtained. X-ray diffraction analysis revealed that the BSCS-Ca x -L ceramics consisted of three phases. The incorporation of Ca 2+ ions did not introduce any new phases. Scanning electron microscopy images showed that the doping of Ca 2+ promoted the grain growth of BSCS-Ca x -L ceramics. Raman spectra were used to investigate the lattice vibrations and crystal structure properties. Energy-dispersive spectroscopy point scans of ceramic samples co-fired with Ag showed that the BSCS-Ca x -L ceramics did not react with Ag, and thus ceramics were chemically compatible with Ag. The best microwave dielectric properties of BSCS-Ca x -L ceramics, including ε r = 7.84, Q×f = 42,500 GHz, and τ f = −16 ppm⋅°C −1 , were obtained at an optimized value of x = 0.02.