We demonstrate the potential of metallurgical controlling of the phase separation reaction, by means of spark plasma sintering consolidation and subsequently controlled heat treatments sequence, for enhancement the thermoelectric properties of the p -type Ge 0.87 Pb 0.13 Te composition. Very high ZT s of up to ∼ 2, attributed to the nucleation of sub-micron phase separation domains and to comparable sized twinning and dislocation networks features, were observed. Based on the experimentally measured transport properties, combined with the previously reported phase separated n -type (Pb 0.95 Sn 0.05 Te) 0.92 (PbS) 0.08 composition, a maximal effi ciency value of ∼ 11.5% was theoretically calculated. These ZT and effi ciency values are among the highest reported for single composition non-segmented bulk material legs.
Methods for enhancement of the direct thermal to electrical energy conversion efficiency, upon development of advanced thermoelectric materials, are constantly investigated mainly for efficient implementation of thermoelectric devices in automotive vehicles, for converting the waste heat generated in such engines into useful electrical power and thereby reduction of the fuel consumption and CO2 emission levels. It was recently shown that GeTe based compounds and specifically GeTe-PbTe rich alloys are efficient p-type thermoelectric compositions. In the current research, Bi2Te3 doping and PbTe alloying effects in GexPb1-xTe alloys, subjected to phase separation reactions, were investigated for identifying the phase separation potential for enhancement of the thermoelectric properties beyond a pure alloying effect. All of the investigated compositions exhibit maximal dimensionless figure of merit, ZT, values beyond 1, with the extraordinary value of 2.1 found for the 5% Bi2Te3 doped-Ge0.87Pb0.13Te composition, considered as among the highest ever reported.
In an attempt to enhance the thermal to electrical conversion efficiency, novel complicated thermoelectric alloys are constantly reported. Most of these reports, correlate the low lattice thermal conductivity values, attributing to the enhanced efficiencies, to nanofeatures apparent in their systems. Yet, since most of the highly efficient thermoelectric materials ever reported are based on complicated alloys, a major reduction of the lattice thermal conductivity can be solely attributed to alloying/disordering effects. The current manuscript, explores by combined experimental and theoretical, using density functional theory and analytical modeling, approaches the lattice thermal conductivity values originated solely by alloying/disordering effects in the highly thermoelectrically efficient p‐type GexPb1–xTe alloys. By comparing these calculated results to various reported experimental values following different synthesis routes, it is shown that solution‐treated samples fit well to the calculated values while for phase‐separated samples, a significant lattice thermal conductivity reduction of ∼50% might be expected.
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