Laser Raman spectroscopic study of ferroelastic LiCsSO4

Chary, BR and Bhat, HL and Chandrasekhar, P and Narayanan, PS (1985) Laser Raman spectroscopic study of ferroelastic LiCsSO4. In: Pramana, 24 (4). pp. 545-557.

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Abstract

Lithium caesium sulphate has been reported to undergo a phase transition from the room temperature orthorhombic phase with space groupP cmn to a final phase with space groupP 22/n. Though a sharp anomaly in its physical properties has been found at 202.0;K, it was found that there was a need for careful investigations in the vicinity of 240 and 210.0;K. Since the changes in the crystal structure involve primarily a rotation of the SO4 tetrahedron about thec-axis and as this may be reflected both in the intensity and polarisation of the internal as well as external phonon modes, the laser Raman spectra of oriented single crystals of LiCsSO4 at different temperatures were investigated. For correlation and definite identification of the spectral features, its infrared absorption spectrum was also studied. An analysis of the intensities and polarizations of the internal modes of the sulphate ions reveals the change in symmetry of the crystal. The integrated intensity and peak height of thev 1 line, plotted against temperature show anomalous peaks in the region of the phase transition. Differential scanning calorimetric study gives the enthalpy change ΔH across the phase transition to be 0.213 kJ/mol.

Item Type:	Journal Article
Publication:	Pramana
Publisher:	Springer Link
Additional Information:	Copyrirht of this article belongs to Springer Link.
Keywords:	Ferroelastic; structural phase transition; total integrated intensity; fluctuations; differential scanning calorimetry
Department/Centre:	Division of Physical & Mathematical Sciences > Physics
Date Deposited:	29 Jan 2010 09:54
Last Modified:	19 Sep 2010 05:44
URI:	http://eprints.iisc.ac.in/id/eprint/23111

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