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Transition of synthetic chromium oxide gel to crystalline chromium oxide: a hot‐stage Raman spectroscopic study
Author(s) -
Yang Jing Jeanne,
Cheng Hongfei,
Martens Wayde N.,
Frost Ray L.
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.2794
Subject(s) - raman spectroscopy , chromium , oxide , amorphous solid , chemistry , thermogravimetric analysis , analytical chemistry (journal) , chromia , materials science , inorganic chemistry , crystallography , organic chemistry , physics , optics
Chromium oxide gel material was synthesised and appeared to be amorphous in X‐ray diffraction study. The changes in the structure of the synthetic chromium oxide gel were investigated using hot‐stage Raman spectroscopy based upon the results of thermogravimetric analysis. The thermally decomposed product of the synthetic chromium oxide gel in nitrogen atmosphere was confirmed to be crystalline Cr 2 O 3 as determined by the hot‐stage Raman spectra. Two bands were observed at 849 and 735 cm −1 in the Raman spectrum at 25 °C, which were attributed to the symmetric stretching modes of OCr III OH and OCr III O. With temperature increase, the intensity of the band at 849 cm −1 decreased, while that of the band at 735 cm −1 increased. These changes in intensity are attributed to the loss of OH groups and formation of OCr III O units in the structure. A strongly hydrogen‐bonded water HOH bending band was found at 1704 cm −1 in the Raman spectrum of the chromium oxide gel; however, this band shifted to around 1590 cm −1 due to destruction of the hydrogen bonds upon thermal treatment. Six new Raman bands were observed at 578, 540, 513, 390, 342 and 303 cm −1 attributed to the thermal decomposed product Cr 2 O 3 . The use of the hot‐stage Raman spectroscopy enabled low‐temperature phase changes brought about through dehydration and dehydroxylation to be studied. Copyright © 2010 John Wiley & Sons, Ltd.