Physical properties of Al doped BiFeO3 obtained by sol-gel route and two-step sintering process

Abstract In this work, structures, photo-absorption, characteristics, and electrical properties of Al-doped BiFeO3 were experimentally investigated in powder and in bulk states. BiFe1-mAlmO3 (m = 0, 2%, 4%, 6% and 8%) powders and ceramics were synthesized by sol-gel method followed by two-step sintering to yield products, which were denoted as A-0, A-2, A-4, A-6, and A-8, respectively. X-ray diffraction (XRD) showed that Al-doped powders and ceramics maintained their rhombic perovskite structures. Scanning electron microscopy (SEM) results confirmed that average grain size of as-prepared ceramics were preserved below micron-level because of the two-step sintering process. By comparison, grain size of Al-doped ceramics were maintained at about 0.6 μm. Optical bandgaps of powders estimated from UV–vis absorbance spectroscopy and Tauc relationship illustrated values that varied from 1.85 eV to 2.05 eV becaused of the Moss-Burstein effect. Leakage current densities declined by 2–3 orders of magnitude, indicating significantly increased resistivity due to Al-doping cause liquid phase segregation. Dielectric and ferroelectric properties also improved. However, dielectric loss decreased and breakdown voltage increased. The resistivity, coercive field (2Ec), and residual polarization intensity (2Pr and ΔP) of A-4 ceramic were recorded as 3.71 × 106 Ω m, 43.7 kV/cm, 1.93 and 1.28 μC/cm2, respectively. In sum, modified BFO appears to be a promising new way to fabricate intensive devices.