Panoptic overview of morphotropic phase boundary in improving ferroelectric properties of Gd doped bismuth ferrite

Bismuth ferrite has the benefit of being a room-temperature multiferroic material; however, it encounters a significant hurdle in the form of leakage current, which hinders its practical application. In this study, we employed Gd doping (up to 10 %) to improve the ferroelectric properties of bismuth ferrite. In addition to lattice distortion leading to phase transitions, Gd doping reduces the average crystallite size because of its smaller ionic radius. The difference in electronegativity between Bi and Gd improves the internal electric field, which is vital for enhancing spontaneous polarisation. At 8 % Gd, a mixed phase of rhombohedral (82 %) and orthorhombic (18 %) phase was observed, which was not seen in lower doping concentrations, indicating the onset of phase transition at this doping concentration. A combination of space charge limited conduction (SCLC) (up to 4 V) and Poole–Frankel (PF) conduction (above 4 V) mechanism was observed in the 8 % Gd doped film. A noticeable enhancement of the ferroelectric properties was observed with the 8 % Gd-doped film, which exhibited superior remnant polarisation (19 μC/cm²) and saturation of polarisation with leakage current around 1.6 nA in comparison with other doping concentrations. This study demonstrates the potential of leveraging the morphotropic phase boundary to improve the ferroelectric properties of Gd-doped BFO while simultaneously offering prospects for enhancing the magnetic properties owing to the inherent magnetic properties of Gd.