Structure evidence of Pna2_1 phase and field-induced transition of Pna2_1/R3c in Bi_(1-x)Sm_xFe_(0.99)Ti_(0.01)O_3 ceramics

摘要

In this study, the structure evidence of the Pna2_1 phase and the field-induced transition of Pna2_1/R3c have been quantitatively investigated in Bi_(1-x)Sm_xFe_(0.99)Ti_(0.01)O_3 (x = 0.12, 0.14, and 0.16) ceramics together with the subsequent electric field-controlled magnetism. A sequential phase transition of R3c-Pna2_1-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 Pna2_1 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 Pna2_1 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 magnetoelec-tric coupling is enhanced, and the linear magnetoelectric coefficient α_(ME) up to 0.91 mV/Oe•cm is obtained in Bi_(1-x)Sm_xFe_(0.99)Ti_(0.01)O_3 ceramics. More importantly, the R3c and Pna2_1 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 Pna2_1 structures.