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Evidences of the evolution from solid solution to surface segregation in Ni‐doped SnO 2 nanoparticles using Raman spectroscopy
Author(s) -
Aragón F. H.,
Coaquira J. A. H.,
Hidalgo P.,
da Silva S. W.,
Brito S. L. M.,
Gouvêa D.,
Morais P. C.
Publication year - 2011
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.2802
Subject(s) - raman spectroscopy , crystallite , tetragonal crystal system , materials science , rutile , analytical chemistry (journal) , doping , solid solution , nanoparticle , transmission electron microscopy , chemical engineering , crystallography , nanotechnology , crystal structure , chemistry , optics , physics , optoelectronics , chromatography , metallurgy , engineering
Abstract Ni‐doped SnO 2 nanoparticles, promising for gas‐sensing applications, have been synthesized by a polymer precursor method. X‐ray diffraction (XRD) and transmission electron microscopy (TEM) data analyses indicate the exclusive formation of nanosized particles with rutile‐type phase (tetragonal SnO 2 ) for Ni contents below 10 mol%. The mean crystallite size shows a progressive reduction with the Ni content. Room‐temperature Raman spectra of Ni‐doped SnO 2 nanoparticles show the presence of Raman active modes and modes activated by size effects. From the evolution of the A 1 g mode with the Ni content, a solubility limit at ∼2 mol% was estimated. Below that content, Raman results are consistent with the occurrence of solid solution (ss) and surface segregation (seg.) of Ni ions. Above ∼2 mol% Ni, the redshift of A 1 g mode suggests that the surface segregation of Ni ions takes place. Disorder‐activated bands were determined and their integrated intensity evolution with the Ni content suggest that the solid‐solution regime favors the increase of disorder; meanwhile, that disorder becomes weaker as the Ni content is increased. Copyright © 2010 John Wiley & Sons, Ltd.