Raman scattering spectra and ferroelectric properties of Bi₁-ₓNdₓFeO₃ (x= -0.2) multiferroic ceramics

Abstract

Single-phase Bi[sub 1−x]Nd[sub x]FeO₃ (BNFO[sub x])(x=0-0.2) multiferroic ceramics were prepared to study the effects of Nd substitution on their crystal structures, Raman scattering spectra, and ferroelectric properties. Rietveld refinement of x-ray diffraction data showed a gradual change in crystal structure from rhombohedral to pseudotetragonal via triclinic with increasing x. The evolvement of Raman normal modes with increasing x suggested that such structural change is accompanied by the weakening of long-range ferroelectric order. The simultaneous occurrence of abrupt mode evolvement and ferroelectric-paraelectric transition in BNFO[sub x=0.175] and BNFO[sub x=0.2] was explained according to the change of Bi-O covalent bonds as a result of the decline in the stereochemical activity of the Bi lone electron pair at 0.175≤x≤0.2.