Abinitio determination of crystal structures of the thermoelectric material MgAgSb

Melanie J. Kirkham, Antonio M. Dos Santos, Claudia J. Rawn, Edgar Lara-Curzio, Jeff W. Sharp, Alan J. Thompson

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98 Scopus citations

Abstract

Materials with the half-Heusler structure possess interesting electrical and magnetic properties, including potential for thermoelectric applications. MgAgSb is compositionally and structurally related to many half-Heusler materials but has not been extensively studied. This work presents the high-temperature x-ray diffraction analysis of MgAgSb between 27 and 420 C, complemented with thermoelectric property measurements. MgAgSb is found to exist in three different crystal structures in this temperature region, taking the half-Heusler structure at high temperatures, a Cu 2Sb-related structure at intermediate temperatures, and a previously unreported tetragonal structure at room temperature. All three structures are related by a distorted Mg-Sb rocksalt-type sublattice, differing primarily in the Ag location among the available tetrahedral sites. Transition temperatures between the three phases correlate well with discontinuities in the Seebeck coefficient and electrical conductivity; the best performance occurs with the novel room temperature phase. For application of MgAgSb as a thermoelectric material, it may be desirable to develop methods to stabilize the room temperature phase at higher temperatures.

Original languageEnglish
Article number144120
JournalPhysical Review B - Condensed Matter and Materials Physics
Volume85
Issue number14
DOIs
StatePublished - Apr 27 2012

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