Structure and dielectric properties of MgO-coated BaTiO₃ ceramics

BaTiO₃@xMgO (BT@xMg, x = 0–7 mol%) ceramics were prepared by MgO-coated BT powders, which were synthesized by a chemical precipitation method. The effects of MgO coating on the phase structure, microstructure and dielectric properties of BT@xMg ceramics were explored. The solid solubility of Mg²⁺ at B-site in BT was about 0.8 mol%, which was confirmed by the c/a ratio variation. When x < 0.8 mol%, the degree of tetragonality and Curie temperature were decreased with the increase of MgO content, and it can be attributed to the B-site substitution of Mg²⁺ ion. At the same time, the decrease in grain size lead to the appearance of Orthorhombic at room temperature. With excess MgO beyond the solid solution limitation (≥ 0.8 mol%), inhomogeneous distribution of Mg was observed around grain boundaries which resulted in a core–shell structure in ceramics. The dielectric temperature stability was effectively improved with a low dielectric loss of ~ 0.01. Furthermore, a weak dependence of dielectric properties on MgO content was observed, where the composites of BT@3 Mg and BT@5 Mg ceramics met X8R standard.