Microstructure, Magnetodielectric, and Multiferroic Properties of xCo_0.8Cu_0.2Fe₂O_4−y(0.8BaTiO₃–0.2BiAlO₃) Composite Ceramics

Herein, xCo_0.8Cu_0.2Fe₂O_4−y (0.8BaTiO₃–0.2BiAlO₃) [xCCFO–y(BTO–BA)] (x = 0, y = 1; x = 1, y = 1; x = 1, y = 2; x = 1, y = 4; x = 1, y = 6) magnetoelectric composite ceramics are synthesized by solid‐state method. The effects of composition on the microstructure, dielectric, ferroelectric and magnetic properties are systematically investigated. Two‐phase structures were confirmed by X‐ray diffraction patterns, which correspond to (BTO–BA) and CCFO phases; a little impurity can be found, and this low‐concentration secondary phase is indexed as BaFe₁₂O₁₉. By scanning electron microscopy, it is found that all the samples show a uniform and relatively dense surface, while the grains show two different kinds of shapes and sizes, which are related with ferroelectric‐phase BTO–BA and magnetic‐phase CCFO. The average grain size of BTO–BA is ≈0.47 μm, and that of CCFO increases with increasing concentration of BTO–BA, and the size of BTO–BA is suppressed with the addition of CCFO. With decreasing the concentration of CCFO, the composites show more and more obvious magnetodielectric effect. The Curie temperature of BTO–BA ceramics is around 150 °C, but this value increases (higher than 150 °C) with the addition of CCFO, implying practical application in high‐temperature devices. The ferroelectric properties of composite ceramics can be optimized by adding BTO–BA.