Crystal Structure and Effective Dielectric Response of Ba 0.5 Sr 0.5 TiO 3 –MgO Composites Synthesized In Situ Process

(1 − x ) Ba 0.5 Sr 0.5 TiO 3 ( BST )– x MgO composite ceramics have been prepared in situ by a citrate–nitrate combustion process, and their crystal structure and effective dielectric response have been investigated systematically. Results reveal that MgO particles homogeneously disperse in BST particles. Rietveld refinement of X ‐ray diffraction data shows that the amount of the incorporation of MgO into BST lattice is increased with increasing the MgO volume fraction ( ƒ M ). It is identified that the incorporation of Mg 2+ into B site gives rise to the formation of F centers in the composites. Related with the incorporation of Mg 2+ into BST lattice, the permittivity of BST in the composite is strongly dependent on ƒ M , which is defined by the relation . Also, the high percolation threshold of ƒ M = 0.60 is observed, which is well in agreement with the theoretical predictions of the modified effective medium approximation coupled with the spherical inclusion model.