Structure evidence of Pna2₁ phase and field-induced transition of Pna2₁/R3c in Bi_1−xSm_xFe_0.99Ti_0.01O₃ ceramics

In this study, the structure evidence of the Pna2₁ phase and the field-induced transition of Pna2₁/R3c have been quantitatively investigated in Bi_1-xSm_xFe_0.99Ti_0.01O₃ (x = 0.12, 0.14, and 0.16) ceramics together with the subsequent electric field-controlled magnetism. A sequential phase transition of R3c-Pna2₁-Pbnm is detected by Rietveld refinement of the x-ray diffraction data. Further, the electric field-induced phase transition is investigated near the morphotropic phase boundary at x = 0.14, where the structure is tuned from Pna2₁ to R3c with poling treatment, and this transition could become reversible with as-annealing after poling. For x = 0.14, the structure is tuned from Pna2₁ to R3c with poling treatment, and this transition could become reversible with as-annealing after poling. The phase transition is confirmed by Rietveld refinements together with VSM measurements, providing an opportunity for electric field-controlled magnetism. The magnetoelectric coupling is enhanced, and the linear magnetoelectric coefficient α_ME up to 0.91 mV/Oe·cm is obtained in Bi_1-xSm_xFe_0.99Ti_0.01O₃ ceramics. More importantly, the R3c and Pna2₁ structures are confirmed by selected area electron diffraction and dark-field analysis at x = 0.14, and the high-resolution TEM image demonstrates the coexistence of the R3c and Pna2₁ structures.