E. Cazzanelli et al., Raman study of the phase transitions sequence in pure WO3 at high temperature and in HxWO3 with variable hydrogen content, SOL ST ION, 123(1-4), 1999, pp. 67-74
An extensive investigation of the temperature dependence of Raman spectra h
as been carried out on WO3 powders from room temperature to 800 degrees C.
In particular the orthorhombic-to-tetragonal phase transition occurring at
about 740 degrees C has been studied for the first time. The Raman active m
ode at 710 cm(-1) of the orthorhombic phase disappears from the spectrum at
temperature below the phase transition point and the Raman activity in the
tetragonal phase results very low. A comparative study of hydrogenated tun
gsten bronzes HxWO3 (x less than or equal to 0.23), where the same transiti
on sequence is driven by an increase of the proton concentration from x = 0
to 0.23, reveals similar behaviour of the high frequency Raman active mode
s, which are better resolved due to the weaker anharmonic interactions. (C)
1999 Elsevier Science B.V. All rights reserved.