Enhanced dielectric, ferroelectric, and ferromagnetic properties of 0.7Bi_(1-x)Tm_xFeO_3-0.3BaTiO_3 ceramics by Tm-induced structural modifcation

摘要

In this study, Tm-doped 0.7Bi_(1-x)Tm_xFeO_3-0.3BaTiO_3 (x = 0-0.05) ceramics have been fabricated using traditional solid-phase reactions and their structural, morphological, and dielectric as well as multiferroic properties are investigated. X-ray diffraction and Rietveld refnement indicated the formation of a Tm-modulated mor-photropic phase boundary (MPB) from the rhombohedral (R3c) and tetragonal (P4mm) phases to a single P4mm phase for Tm content of x = 0.02-0.03. Tm occupation of lattice sites is strongly suggested at both the A and B sites in the ABO_3-type perovskite structure, which is supported by the obtained Raman spectra, the calculated tolerance factor, and dielectric relaxation characteristics. With the Tm-induced aforementioned-structural modifcation, the dielectric constant, remnant polarization (P_r), and remnant magnetization (M_r) values indicate that the dielectric and multiferroic properties are greatly improved. The obtained maximum remnant polarization (2P_r = 35.28 μC/cm~2) and remnant magnetization (2M_r = 0.56 emu/g) are approximately two and seven times larger, respectively, than those of the sample without Tm substitution (x = 0). With increasing the Tm content, the remnant polarization, and the remnant magnetization exhibit almost the same trends in variation, indicating the possible existence of a relatively strong magnetoelectric coupling effect. Our study may provide a substitution strategy (structural modifcation by substituting the same element into two different lattice sites) to effciently enhance the dielectric and multiferroic properties of BiFeO_3-BaTiO_3-based ceramics.