Structural transformation and multiferroic properties of Sm and Ti co-doped BiFeO3 ceramics with Fe vacancies

Sm and Ti co-doped BiFeO3 (BFO) ceramics with Fe vacancies-Bi0.86Sm0.14FeO3, Bi0.86Sm0.14Fe0.99Ti0.01O3, and Bi0.86Sm0.14Fe0.9Ti0.05O3-were prepared by a solid-state method using a rapid liquid process. X-ray diffraction indicated that all samples exhibited a rhombohedral structure with a minor secondary phase. The structural transformation from a rhombohedral (space group: R3c) to orthorhombic structure (space group: Pnma) was observed in the sample of Bi0.86Sm0.14Fe0.9Ti0.05O3, which was also confirmed by Raman scattering spectra. Microstructural investigations with scanning electron microscopy showed a reduction in grain size with doping of BFO. The dielectric loss of Bi0.86Sm0.14Fe0.9Ti0.05O3 reaches 0.05 (at 100 Hz) owing to the introduction of Ti and Fe vacancies. Ferroelectromagnetic measurements revealed the existence of ferroelectricity with a remanent polarization of 0.24 µC/cm2 in Bi0.86Sm0.14FeO3, paraelectricity in Bi0.86Sm0.14Fe0.9Ti0.05O3, and weak ferromagnetism with a remanent magnetization of 0.2 emu/g in Bi0.86Sm0.14Fe0.99Ti0.01O3. The two composition-driven phases exist simultaneously and the different coercive field might be related to the jumps in the ferromagnetic hysteresis loops. Both the ferroelectric and magnetic properties were shown to correlate with the composition-driven structural evolution.