Electronic texture of the thermoelectric oxide Na0.75CoO2
Abstract
From 59Co and 23Na NMR, we demonstrate the impact of the Na+ vacancy ordering on the cobalt electronic states in Na0.75CoO2: at long time scales, there is neither a disproportionation into 75 % Co3+ and 25 % Co4+ states, nor a mixed-valence metal with a uniform Co3.25+ state. Instead, the system adopts an intermediate configuration in which 30 % of the lattice sites form an ordered pattern of localized Co3+ states. Above 180 K, an anomalous mobility of specific Na+ sites is found to coexist with this electronic texture, suggesting that the formation of the latter may contribute to stabilizing the Na+ ordering. Control of the ion doping in these materials thus appears to be crucial for fine-tuning of their thermoelectric properties.
Keywords
Cite
@article{arxiv.0801.4095,
title = {Electronic texture of the thermoelectric oxide Na0.75CoO2},
author = {M. -H. Julien and C. de Vaulx and H. Mayaffre and C. Berthier and M. Horvatic and V. Simonet and J. Wooldridge and G. Balakrishnan and M. R. Lees and D. P. Chen and C. T. Lin and P. Lejay},
journal= {arXiv preprint arXiv:0801.4095},
year = {2008}
}
Comments
4 pages, to appear in Phys. Rev. Lett