Nature of the cubic to rhombohedral structural transformation in (AgSbTe2)(15)(GeTe)(85) thermoelectric material

TitleNature of the cubic to rhombohedral structural transformation in (AgSbTe2)(15)(GeTe)(85) thermoelectric material
Publication TypeJournal Article
Year of Publication2007
AuthorsCook BA, Kramer MJ, Wei X, Harringa JL, Levin EM
Journal TitleJournal of Applied Physics
Volume101
Pages053715
Date PublishedMar
Type of ArticleArticle
ISBN Number0021-8979
Accession NumberISI:000244945400076
KeywordsCONDUCTIVITY, CONVERSION, FIGURE, GETE, merit, resistivity
Abstract

The existence of a large thermoelectric figure of merit in (AgSbTe2)(15)(GeTe)(85) has been known for many years. However, the nature of the crystallographic transformation in these materials from a high-temperature cubic to a low-temperature rhombohedral polymorph and its effect on electrical transport has not been clearly established. Transmission electron microscopy studies were performed that show extensive twinning in the low-temperature structure, resulting from lattice strain during the dilation along the (111) crystallographic direction. Analysis of differential scanning calorimetric studies indicates that the transformation is of second order, so that the high-temperature cubic phase is nonquenchable. High-temperature x-ray diffraction was performed to establish the transformation temperature, which was found to be complete upon heating at a temperature of 510 K. Results of electrical conductivity measurements as a function of temperature on as-cast samples are discussed in terms of the observed twinning. (c) 2007 American Institute of Physics.

DOI10.1063/1.2645675
Alternate JournalJ. Appl. Phys.