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Improved Thermoelectric Properties in Melt-Spun SnTe
SnTe has been the
focus of numerous experimental and theoretical
studies over the last years owing to its high thermoelectric performances
near 800 K when appropriately doped. Here, we demonstrate that melt-spinning,
an ultrafast-quenching synthesis technique, followed by spark plasma
sintering results in enhanced <i>ZT</i> values in polycrystalline
SnTe. To illustrate the impact of this technique, the results are
contrasted with those obtained on two polycrystalline samples prepared
by direct quenching of molten SnTe and without quenching. SnTe melt-spun
ribbons are characterized by a peculiar columnar microstructure that
contributes to lower the lattice thermal conductivity below 700 K
in pressed samples. More importantly, this technique results in a
significant decrease in the hole concentration, giving rise to enhanced
thermopower values above 500 K. The variation in the hole concentration
is likely due to a slight loss of elemental Te during the melt-spinning
process. Thanks to the decreased hole concentration, the thermoelectric
performances are significantly enhanced with a peak <i>ZT</i> value of 0.6 at 800 K, which represents a 40% increase over the
values measured for samples prepared with and without quenching. These
findings indicate that melt-spinning provides a novel strategy to
improve the thermoelectric properties of SnTe that could be worthwhile
extending to substituted compounds