Modulation of the electric and magnetic properties by Ti non-stoichiometry in 0.70BiFeO₃-0.30BaTi_x O₃ceramics

The modulation of the structure and dielectric, ferroelectric, and magnetic properties by Ti non-stoichiometry in 0.70BiFeO3-0.30BaTixO3 (BF30BT-x, x = 0.85-1.15) ceramics was studied systematically. In Ti-rich samples, excessive Ti mainly exists in the form of an impurity Aurivillius phase, and so except that the impurity phase reduces the resistance, the structure, morphology, Curie temperature (TC ∼390 °C), and ferroelectricity in Ti-rich ceramics are similar to those in stoichiometric ceramics (BF30BT-1.00). In Ti-poor samples, the appropriate Ti-poor concentration appears in the BF30BT-0.90 ceramic, and the structure becomes the coexistence of the rhombohedral phase and the pseudo-cubic phase (R+PC). The ferroelectric phase transition becomes a frequency-independent normal phase transition, and TC is greatly increased (553 °C). The hysteresis loop becomes more saturated, and a large internal bias field (Ei = 4.5 kV/cm) appears. For magnetic properties, all samples display a weak ferromagnetic nature, and as x increases, Mr and Mmax increase nearly linearly.