Dielectric and multiferroic properties of 0.8BaTiO3-0.2BiAlO3/Co0.8Cu0.2Fe2O4 composite ceramics

0.8BaTiO3-0.2BiAlO3/Co0.8Cu0.2Fe2O4 composite ceramics with a molar ratio of 6:1 were prepared by hydrothermal method combined with solid-state method, and effects of the sintered temperature and time on the microstructure, dielectric, ferroelectric, and magnetic properties were investigated. XRD result indicates that the composite ceramics show bi-phase structure, and the secondary phase is indexed as Ba3Fe32O51, and proves that we can change the sintered temperature and sintered time to adjust the crystallinity of the composite ceramics and the concentration of impurities. The surface is relatively uniform except for few pores, and the grain size of ferromagnetic phase increases as the function of temperature and time. The dielectric dispersion of composite ceramics is obtained, and the character comes from inhomogeneous structure and Maxwell–Wagner type interfacial polarization. The two peaks of dielectric constant are obtained, and the composite ceramics (1200 °C/4 h) show high dielectric constant and loss due to the interface effect, and this result is confirmed by the AC conductively. The relaxation result is different from the ferroelectric phase, and this may be caused by the thermally activated, the grain size of ferroelectric phase, impurity phase, pore, and defect of composite ceramics. The ferromagnetic result refers that the sintered temperature has obvious influence on the coercive force by the grain size and magnetic anisotropy.