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Structural transformations in Pb 1 − x Bi 4 + x Ti 4 − x Mn x O 15 ( x = 0.2 and 0.4): a Raman scattering study
Author(s) -
Prasetyo Anton,
Mihailova Boriana,
Suendo Veinardi,
Nugroho A. A.
Publication year - 2017
Publication title -
journal of raman spectroscopy
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.748
H-Index - 110
eISSN - 1097-4555
pISSN - 0377-0486
DOI - 10.1002/jrs.5030
Subject(s) - aurivillius , crystallography , octahedron , raman spectroscopy , chemistry , raman scattering , perovskite (structure) , phase transition , phase (matter) , ferroelectricity , crystal structure , materials science , condensed matter physics , dielectric , physics , optics , optoelectronics , organic chemistry
The temperature evolution of the Raman scattering of Pb 1 − x Bi 4 + x Ti 4 − x Mn x O 15 ( x = 0.2 and 0.4) on cooling from 850 to 140–130 K was studied in order to elucidate the effect of B ‐site Mn 3+ doping accompanied by the increase in the A ‐site Bi 3+ content on the structural transformations in four‐layer Aurivillius‐type compound ( A n − 1 Bi 2 B n O 3 n + 3 , n = 4). The ferroelectric–paraelectric transition ( T c ~800 K for x = 0.2 and ~765 K for x = 0.4) is well mirrored by the Raman scattering near 60 cm −1 arising from the so‐called rigid layer mode. The temperature dependence of the phonon mode near 42 cm −1 arising from A ‐site Pb/Bi displacements indicates a second structural transformation near 570 K and 400 K for x = 0.2 and 0.4, respectively, similar to that observed for Mn‐free PbBi 4 Ti 4 O 15 . This structural alteration resembles a thermodynamically second‐order phase transition for all three compounds and the critical temperature ( T a ) decreases with the increase in the A ‐site Bi 3+ amount, related to the heterovalent substitution (Mn 3+ for Ti 4+ ) on the B site; T a = 600, 570, 400 K for x = 0, 0.2, 0.4, respectively. The B O 6 tilting and bending mode near 220 cm −1 also shows an anomaly at T a , and, thus, this second structural transformation was attributed to subtle rearrangements of A ‐site cations accompanied by octahedral B O 6 tilting in the perovskite‐like blocks. Copyright © 2016 John Wiley & Sons, Ltd.