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A1: Low temperature materials
The lack of efficient thermoelectric materials for cryogenic applications motivates research in new materials that are optimized to perform from 80-300 K. PtSb2 is a very narrow gap semiconductor for which previous work revealed a large Seebeck coefficient at low temperature. An investigation of PtSb2 was performed to maximize the power factor at low temperatures. It was found that nominally undoped and stoichiometric PtSb2 has a positive Seebeck coefficient which peaks at 230 μV/K. A range of compositions of PtSb2-xTex ; x = 0.0002 to x=0.04 were examined. At all tellurium dopant concentrations the Seebeck coefficient was found to be negative and readily dependent in magnitude on the concentration. The highest magnitude of Seebeck coefficient seen in these concentrations was found in PtSb2-xTex where x = 0.0005. The compositions Pt1-x Fex Sb2 and Pt1-x Ybx Sb2 were also examined and found to show an increase in power factor and ZT across a wide range of low temperatures. These results inspire further investigation of this material to find the concentration of tellurium, iron, and ytterbium which will maximize power factor and could lead to high thermoelectric performance in the cryogenic range.
