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Probing the ferroelectric phase transition in sol–gel‐derived polycrystalline bismuth ferrite thin films
Author(s) -
Kumar Ashok,
Murari N. M.,
Katiyar R. S.
Publication year - 2008
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.1984
Subject(s) - raman spectroscopy , bismuth ferrite , crystallite , materials science , ferroelectricity , thin film , analytical chemistry (journal) , phase transition , differential thermal analysis , phonon , dielectric , diffraction , chemistry , optics , condensed matter physics , multiferroics , nanotechnology , optoelectronics , chromatography , physics , metallurgy
Polycrystalline BiFeO 3 (BFO) thin films were successfully grown on Pt/Ti/SiO 2 /Si(100) and SrTiO 3 (STO) (100) substrates using the chemical solution deposition (CSD) technique. X‐ray diffraction (XRD) patterns indicate the polycrystalline nature of the films with rhombohedrally distorted perovskite crystal structure. Differential thermal analysis (DTA) was performed on the sol–gel‐derived powder to countercheck the crystal structure, ferroelectric (FE) to paraelectric (PE) phase transition, and melting point of bismuth ferrite. We observed a significant exothermic peak at 840 °C in DTA graphs, which corresponds to an FE–PE phase transition. Raman spectroscopy studies were carried out on BFO thin films prepared on both the substrates over a wide range of temperature. The room‐temperature unpolarized Raman spectra of BFO thin films indicate the presence of 13 Raman active modes, of which five strong modes were in the low‐wavenumber region and eight weak Raman active modes above 250 cm −1 . We observed slight shifts in the lower wavenumbers towards lower values with increase in temperature. The temperature‐dependent Raman spectra indicate a complete disappearance of all Raman active modes at 840 °C corresponding to the FE–PE phase transitions. There is no evidence of soft mode phonons. Copyright © 2008 John Wiley & Sons, Ltd.