Structure evidence of Pna21 phase and field-induced transition of Pna21/R3c in Bi1−xSmxFe0.99Ti0.01O3 ceramics

Abstract

In this study, the structure evidence of the Pna21 phase and the field-induced transition of Pna21/R3c have been quantitatively investigated in Bi1-xSmxFe0.99Ti0.01O3 (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 αME up to 0.91 mV/Oe·cm is obtained in Bi1-xSmxFe0.99Ti0.01O3 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.