Structure, ferroelectric, ferromagnetic, and piezoelectric properties of Al-modified BiFeO3-BaTiO3multiferroic ceramics

0.725BiFe1−xAlxO3–0.275BaTiO3 + 1 mol% MnO2 ceramics were prepared by a conventional ceramic technique. The effects of Al doping and sintering temperature on microstructure, piezoelectricity and magnetism of the ceramics were studied. The crystalline structures of BFO-BT-BA-x ceramics sintered at 970 °C for 2 h evolve from rhombohedral structure at x = 0 to the coexistence of rhombohedral structure and orthorhombic phases at x = 0.01–0.03 and finally to orthorhombic phases at x > 0.03. The critical sintering temperature is 970 °C. For the ceramics with x = 0.01 sintered at/above 970 °C, large grains, good densification, high resistivity, and enhanced ferromagnetic properties are obtained. The ceramic with x = 0.01 sintered at 970 °C possesses high resistivity (∼109 Ω cm) and good piezoelectric properties (d33 = 138 pC N−1, kp = 32.7%). Al doping decreases the ferromagnetic properties of the ceramics, while the increase in the sintering temperature enhances the ferromagnetic properties of the ceramics.