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Title: Electronic and thermal transport in GeTe: A versatile base for thermoelectric materials

GeTe is a narrow-band gap semiconductor, where Ge vacancies generate free charge carriers, holes, forming a self-dopant degenerate system with p-type conductivity, and serves as a base for high-performance multicomponent thermoelectric materials. There is a significant discrepancy between the electronic and thermal transport data for GeTe-based materials reported in the literature, which obscures the baseline knowledge and prevents a clear understanding of the effect of alloying GeTe with various elements. A comprehensive study including XRD, SEM, EDS, Seebeck coefficient, electrical resistivity, thermal conductivity, and {sup 125}Te NMR of several GeTe samples was conducted. Similar Seebeck coefficient and electrical resistivity are observed for all GeTe samples used showing that the concentration of Ge vacancies generating charge carriers is constant along the ingot. Very short {sup 125}Te NMR spin-relaxation time agrees well with high carrier concentration obtained from the Hall effect measurements. Our data show that at ∼700 K, GeTe has a very large power factor, 42 μWcm{sup −1}K{sup −2}, much larger than that of any high efficiency thermoelectric telluride at these temperatures. Electronic and thermal properties of GeTe are compared to PbTe, another well-known thermoelectric material, where free charge carriers, holes or electrons, are generated by vacancies on Pb or Temore » sites, respectively. Discrepancy in the data for GeTe reported in literature can be attributed to the variation in the Ge:Te ratio of solidified samples as well as to different conditions of measurements.« less
Authors:
 [1] ;  [2] ; ;  [1]
  1. Division of Materials Sciences and Engineering, Ames Laboratory U.S. DOE, Iowa State University, Ames, Iowa 50011 (United States)
  2. (United States)
Publication Date:
OSTI Identifier:
22218099
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Applied Physics; Journal Volume: 114; Journal Issue: 8; Other Information: (c) 2013 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; 75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY; CARRIER DENSITY; CHARGE CARRIERS; CHEMICAL ANALYSIS; ELECTRIC CONDUCTIVITY; GERMANIUM TELLURIDES; HALL EFFECT; LEAD TELLURIDES; NUCLEAR MAGNETIC RESONANCE; POWER FACTOR; RELAXATION TIME; SCANNING ELECTRON MICROSCOPY; SEMICONDUCTOR MATERIALS; TELLURIUM 125; THERMAL CONDUCTIVITY; THERMOELECTRIC MATERIALS; VACANCIES; X-RAY DIFFRACTION