Sintering behaviour and microwave dielectric properties of MgO-2B₂O₃-xwt%BaCu(B₂O₅)-ywt%H₃BO₃ ceramics

This study investigates the bulk density, sintering behaviour, and microwave dielectric properties of the MgO-2B₂O₃ series ceramics synthesised by solid-state reaction. According to the X-ray diffraction and microstructural analyses, the as-prepared MgO-2B₂O₃ ceramics possess a single-phase structure with a rod-like morphology. The effects of different quantities of H₃BO₃ and BaCu(B₂O₅) (BCB) on the bulk density, sintering behaviour, and microwave dielectric properties of the MgO-2B₂O₃ ceramics were investigated. Accordingly, the optimal sintering temperature was obtained by adding 30 wt% H₃BO₃ and 8 wt% BCB. We also reduced the sintering temperature to 825 ℃. Furthermore, the addition of 40 wt% H₃BO₃ and 4 wt% BCB increased the quality factor, permittivity, and temperature coefficient of resonance frequency of MgO-2B₂O₃ to 44,306 GHz (at 15 GHz), 5.1, and -32 ppm/℃, respectively. These properties make MgO-2B₂O₃ a viable low- temperature co-fired ceramic with broad applications in microwave dielectrics.