Abstract
Because of the increasing demand for energy and the resulting environmental problems, it is necessary to look for an alternative energy source that is economically and environmentally appropriate. Ferroelectric and multiferroic materials have attracted significant interest and could prove promising for photovoltaic applications. Here, we report the structural evolution and its relationship with the optical, magnetic, and ferroelectric properties of Ba0.92Bi0.08Ti(1-x)CoxO3, abbreviated as BBT:Cox (0 <= x <= 0.08) ceramic prepared by a solid-state reaction technique. Refinement analyses of X-ray data show that incorporating Co ions into the Ti sites of BBT host lattices gives rise to a single tetragonal phase with no evidence of a secondary phase. Direct evidence of Ti3+ surface defects and oxygen vacancies has been carried out via an XPS study. The optical research showed that the BBT bandgap was successfully tuned from 3.21 to 2.61 eV. The tuning in bandgap is explained based on the charge compensation and octahedral distortion mechanisms. In the room-temperature magnetic properties measurements, the pure BBT sample is diamagnetic, whereas the BBT:Cox sample is ferromagnetic. The reversible polarization induced by an electric field indicates the ferroelectric character of the ceramics at room temperature. The results obtained in this work may help construct intrinsic multiferroics to develop photovoltaic devices for next-generation applications.