2003/04/21 by F. Rivadulla, J. S. Zhou, Jianshi Zhou +2 · 3 citations
Materials Science · Physics and Astronomy · #Advanced Condensed Matter Physics #Advanced Thermoelectric Materials and Devices #Thermal Expansion and Ionic Conductivity #cond-mat.mtrl-sci #cond-mat.str-el
paper · pdf · doi:10.1103/physrevb.68.075108
11 pages, 7 figures, submitted to Phys. Rev. B
arxiv created 2003/04/21 · openalex publication_date 2003/08/14 · arxiv updated 2009/11/30 · openalex created_date 2016/06/24 · openalex updated_date 2026/07/28
We report measurements of room-temperature compressibility, thermal expansion, thermoelectric power \ensuremathα(T) at various pressures P<~20kbar, basal-plane resistivity \ensuremathρab(T), magnetic susceptibility, and thermal conductivity \ensuremathκ(T) taken on single-crystal or cold-pressed Na_1\ensuremath-xCoO2, (1\ensuremath-x)\ensuremath≈0.57. Whereas the c-axis thermal expansion is large, the basal-plane thermal expansion remains negligible for all temperatures T<300K. We propose here that pinning of the nominal Co(IV)/Co(III) redox couple at the top of the O^2\ensuremath-:2p6 bands, and a schematic location of the a1T and eT antibonding bands of this couple with respect to the Fermi energy are responsible for the large thermoelectric power found in this compound. On the other hand, the phonon contribution to the thermal conductivity measured on a dense cold-pressed ceramic sample is not as small as previously reported.