Microstructure and dielectric responses of Ba0.5Sr0.5TiO3–Mg2TiO4 composites synthesized by using a citrate gel in situ process

• pH 7 precursor was suitable for the formation of Ba1−xSrxTiO3 and Mg2TiO4 biphase.
• Curie temperature of the composites was close to or even higher than that of pure Ba1−xSrxTiO3.
• Permittivity of Ba1−xSrxTiO3 in the composite was strongly dependent on Mg2TiO4 volume fraction.
• The samples with compositions of 0.5 ≤ ƒMT ≤ 0.7 exhibited percolation transition.

(1 − x)Ba0.5Sr0.5TiO3(BST)–xMg2TiO4(MT) composite ceramics have been prepared in situ by using a citrate–nitrate combustion process. X-ray diffraction data showed that neutral precursor with pH 7 is suitable for in situ formation of biphase structure with BST and MT. Curie temperature of the composite ceramics sintered at 1300 °C was close to or even higher than that of pure BST. Modeling with the modified effective medium approximation indicated that permittivity of BST in the composite was strongly dependent on the MT volume fraction (fMT), which can be described by the relation ϵBST=a×eb×fMTϵBST=a×eb×fMT. The samples with compositions of 0.5 ≤ fMT ≤ 0.7 exhibited percolation transition.

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