Infrared spectroscopy of superionic conductor LiNaSO4: Vibrational modes and thermodynamics

Zhang, M. and Putnis, A. and Salje, E. K. H. (2006) Infrared spectroscopy of superionic conductor LiNaSO4: Vibrational modes and thermodynamics. Solid State Ionics, 177 (1-2). pp. 37-43. DOI 10.1016/j.ssi.2005.10.001

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Abstract

Infrared active phonon spectra of lithium sodium sulphate, LiNaSO4, were studied at temperatures between 20 K and 780 K. Dielectric constant [ε = ε′ + iε″] and energy loss function [− Im(1/ε)] were obtained from Kramers–Kronig analysis. Our IR data show a more complete set of vibrational modes than previous investigations. The IR data of LiNaSO4 at 20 K are consistent with the P31c symmetry, indicating that LiNaSO4 shows no structural phase transitions between 20 K and 300 K, in contrast to LiKSO4. On heating from 20 K, phonon modes related to Li and Na vibrations show a dramatic line broadening and decrease in intensity. An extra mode is recorded near 380 cm− 1 at 500 K. The absorption shows a systematic increase in intensity on further heating. These changes are attributed to anharmonic effects and Li diffusion or hopping. Dramatic spectral changes in the internal modes occur near 620 K on heating, suggesting the onset of the rotational disorder of SO4 tetrahedra, but the Li atom spectrum shows weak response to the rotational disorder.

Item Type: Article
Uncontrolled Keywords: 2006 AREP IA49 IA50 2006 P
Subjects: 03 - Mineral Sciences
Divisions: 03 - Mineral Sciences
Journal or Publication Title: Solid State Ionics
Volume: 177
Page Range: pp. 37-43
Identification Number: 10.1016/j.ssi.2005.10.001
Depositing User: Sarah Humbert
Date Deposited: 16 Feb 2009 13:04
Last Modified: 23 Jul 2013 09:54
URI: http://eprints.esc.cam.ac.uk/id/eprint/834

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