Synthesis of CaAl2xB2O4+3x: Novel microwave dielectric ceramics with low permittivity and low loss

Abstract Novel CaAl2xB2O4+3x (x = 0.25, 0.5, 0.75, and 1) ceramics were prepared via solid-state reaction method. The investigation is concentrated on sintering behavior, phase composition and dielectric properties of CaAl2xB2O4+3x ceramics with various ratios of Al2O3 content. The optimal sintering temperature and the content of CaAl2B2O7 are highly related to the variation of x value. CaAl2xB2O4+3x ceramics possess excellent microwave dielectric properties: er = 5.8 ± 0.05, Q × f = 63,338 ± 2690 GHz (@13.57 GHz), and τf=-29 ± 2 ppm/℃ when sintered at 940 ℃ for x = 0.5. Comparing the properties of CaAl2xB2O4+3x ceramics with reported borate ceramics, the ceramics prepared in this study with low dielectric loss and low sintering temperature have promising prospects in LTCC technology.