Ferroelectric and magnetic properties in (1-x)BiFeO3-x(0.5CaTiO3-0.5SmFeO3) ceramics

Multiferroic ceramics were prepared and characterized in (1-x)BiFeO3-x(0.5CaTiO(3)-0.5SmFeO(3)) system by a standard solid-state reaction process. The structure evolution was investigated by X-ray diffraction and Raman spectrum analyses. The refinement results confirmed the different phase assemblages with varying amounts of polar rhombohedral R3c and nonpolar orthorhombic Pbnm as a function of the substitution content. In the compositions range of 0.2x0.5, polar R3c and nonpolar Pbnm coexisted, which was referred to polar-to-nonpolar morphotropic phase boundary (MPB). According to the dielectric and DSC analysis results, the ceramics with x0.2 changed to diffused ferroelectric, and the ferroelectric properties were enhanced significantly. Two dielectric relaxations were detected in the temperature range of 200-300 K and 500-700 K, respectively. The high-temperature dielectric relaxation was attributed to the grain-boundary effects. While the low temperature dielectric relaxation obtained in the samples with x=0.3-0.5 was related to the charge transfer between Fe2+ and Fe3+. The magnetic hysteresis loops measured at different temperature indicated the enhanced magnetic properties in the present ceramics, which could be attributed to the suppressed cycloidal spin magnetic structure by Ti ions. In addition, the rare-earth Sm spin moments might also affect the magnetic properties at relatively lower temperature.