paper

Raman Phonons and Ageing-Related Surface Disorder in NaxCoO2

arXiv:cond-mat/0308065 · doi:10.1016/j.physc.2003.09.085

Abstract

The polarized Raman spectra from ab and ac surfaces of single crystal NaxCoO2 (x~0.7), parent compound of recently discovered superconductor NaxCoO2.yH2O, are reported and discussed. The crystals were hexagon platelets of typical size 3x3x0.1 mm. Three of the five (A1g+E1g+3E2g) Raman active phonons were unambiguously identified at 458 (E1g), 494(E2g) and 574 (A1g) cm-1. The spectra from ab and ac surfaces differ significantly and provide evidence that within hours after preparation the ac surface, unlike the ab one, is strongly disordered. Within several days the disorder extends over the ab surface too.

4 pages, 1 table, 4 figures. Physica C (accepted 26 September 2003)

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