Mg3B2O6 microwave dielectric ceramics fabricated by combining cold sintering with post-annealing process

It is difficult to get pure-phase Mg 3 B 2 O 6 (abbreviated as MBO) ceramics by the traditional high-temperature solid-state reaction method. In this paper, pure-phase MBO ceramics were successfully densified and obtained by combining the cold sintering and post-annealing process. The relative density of MBO ceramics was ∼80% cold sintered at 150°C/90 min/800 MPa, which was further improved to ∼91% by post-annealing at 900°C, 400°C lower than that of the traditional high-temperature sintering process (∼1300°C). X-ray powder diffraction (XRD), scanning electron microscopy (SEM), and Raman results demonstrated that the secondary phase of MgO was effectively eliminated, and dense microstructure was observed by the cold-sintering process plus post-annealing treatment. Finally, the microwave dielectric properties of MBO were evaluated with ε r : 5.15–6.37, Q×f : 5942–16 686 GHz, τ f : −48.45–69.72 ppm/°C.