In situ synthesis of Ba0.5Sr0.5TiO3–Mg2TiO4 composite ceramics and their effective dielectric response

(1 − x)Ba0.5Sr0.5TiO3 (BST)–xMg2TiO4 (MT) composite ceramics have been prepared in situ by a sol–gel process. Their effective dielectric response has been addressed theoretically in terms of the compound law and the modified effective medium approximation, coupled with the spherical inclusion model. Results show that the permittivity of BST in the composite is strongly dependent on the MT volume fraction (fMT), whether under an electric field or not. Also, the percolation transition behavior of tunability occurs when fMT ⩾ 0.5.