Structure, electrical, dielectric and ferroelectric properties of (1 − x)BiFeO₃ − xAl₂O₃ ceramics

Lead-free ferroelectric composite ceramics of (1 − x)BiFeO₃ − xAl₂O₃ (x = 0.00, 0.02, 0.04, 0.06, 0.08 and 0.10) were synthesized using the traditional solid-state reaction method. The effects of Al₂O₃ addition on structural (crystal data and microstructure), ferroelectric, dielectric properties, and leakage current characteristic were investigated. X-ray diffraction and scanning electron microscopy demonstrated that the addition of Al₂O₃ promoted the formation of the secondary phases (Bi₂Fe₄O₉ and Bi₂₄Al₂O₃₉) and the average grain size significantly reduced from 1.49 μm for x = 0.00 to 0.45 μm for x = 0.10. The samples with Al₂O₃ addition had lower dielectric constant and dielectric loss. The Curie temperature (T_C) decreased gradually from 475 °C for x = 0.02 to 390 °C for x = 0.10. Leakage current density decreased significantly with the addition of the Al₂O₃, and the leakage conduction mechanism was changed from Ohmic relationship to space charge limited conduction (SCLC) mechanism. The ferroelectric hysteresis loops became more typical in shape with the addition of the Al₂O₃.