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Micro‐Raman probing of short‐range disorder in lanthanum‐doped lead titanate films
Author(s) -
Dobal P. S.,
Majumder S. B.,
Bhaskar S.,
Katiyar R. S.
Publication year - 1999
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/(sici)1097-4555(199907)30:7<567::aid-jrs420>3.0.co;2-j
Subject(s) - raman spectroscopy , lanthanum , materials science , lead titanate , doping , titanate , lead (geology) , range (aeronautics) , nanotechnology , ferroelectricity , inorganic chemistry , chemistry , composite material , ceramic , optoelectronics , optics , physics , geology , dielectric , geomorphology
Lanthanum‐modified lead titanate thin films with composition Pb 1− x La x Ti 1− x /4 O 3 , where x = 0.00, 0.05, 0.10, 0.15, 0.20, 0.25 and 0.30, were grown on (0001) sapphire using the sol–gel process. Raman scattering, in the temperature range 75–783 K, was used to probe the phase transition and the possibility of relaxor behavior in these compositions. The x‐ray diffraction measurements indicate a cubic structure for x > 0.15, while the Raman modes were observed up to x = 0.25. The phonon modes exist above the tetragonal‐to‐cubic phase transition temperature in these solid solutions owing to a short‐range structural disorder in the paraelectric cubic phase. The lack of a well defined transition temperature suggested a diffuse nature of the ferroelectric phase transition. An increase in the diffuseness of transitions was evidenced with increasing La content, which indicates the relaxor behavior and also its relationship with the local disorder in these materials. Copyright © 1999 John Wiley & Sons, Ltd.