The interplay of phases, structural disorder and dielectric behavior in Al doped BiFeO3-BaTiO3 ceramics

Al doped BiFeO3-BaTiO3 (BFA-BT) systems with a defined composition were prepared by a conventional solid-state method. From SEM and XRD analyses, the high-density of the ceramics and the high lattice parameters ratio c(T)/a(T) traducing large distortions of the rhombohedral phase play a dominant role in the enhanced piezoelectric properties. The high polarization and large strain were achieved in the BF(0.970)A(0.030)-BT system. Fe-57 Mossbauer spectra revealed the large disorder of Fe3+ at B sites preferentially occupied by more Al3+ doping ions, forming the diffusive phase transition for dielectric behaviors in ceramics. Grain and grain-boundary effects were pointed out from the dielectric modulus and its related thermal evolution. AC capacitances indicated two relaxation processes marked by the grains and interfaces involved in the polycrystalline ceramics for highly doped systems. (C) 2019 Published by Elsevier B.V.