Low-temperature firing and microwave dielectric properties of (1−x)Ca5Mg4(VO4)6-xBa3(VO4)2 temperature stable ceramics

Abstract (1−x)Ca 5 Mg 4 (VO 4 ) 6 -xBa 3 (VO 4 ) 2 (0.5 ≤ x ≤ 0.7) ceramics were fabricated via the conventional solid-state reaction method. The phase composition, microstructure, and compatibility with silver were investigated using X-ray diffraction, Raman spectra and Scanning electron microscopy. The results confirmed that Ca 5 Mg 4 (VO 4 ) 6 and Ba 3 (VO 4 ) 2 crystal phases can be well coexisted in the sintered ceramics. The temperature coefficient of resonant frequency could be tuned by the volume mixture rule of Ca 5 Mg 4 (VO 4 ) 6 and Ba 3 (VO 4 ) 2 . As for the addition of Ba 3 (VO 4 ) 2 , the e r showed to increase, while the Qxf declined. In particular, the 0.35Ca 5 Mg 4 (VO 4 ) 6 -0.65Ba 3 (VO 4 ) 2 composite ceramics sintered at 900 °C for 5 h showed excellent combinational microwave dielectric properties: e r  = 11.9, Qxf = 35 000 GHz, and τ f  = −2 ppm/°C, which also exhibited good chemical compatibility with silver.