A novel composite ceramic with low densification temperature was fabricated using the conventional solid-state method. The XRD and Rietveld refinement results indicated that the two phases of CaB2O4 and CaSiO3 can coexist in all compositions. Furthermore, a phase transition of CaSiO3 ceramic from α-phase to β-phase was observed. A dense ceramic with excellent microwave dielectric properties (εr~6.4, Q × f~75,600 GHz, and a negative τf~26.9 ppm/°C) was obtained at x = 0.5 when sintered at 925 °C at the frequency of 14.2 GHz. A good chemical compatibility between the composite ceramic and Ag electrode was improved by elemental mapping results. A patch antenna was fabricated based on the simulated result. All results indicated that the 0.5 CaB2O4 + 0.5 CaSiO3 ceramic has large application potential in the LTCC field.
