Abstract
Rare-earth (RE) tellurides have been studied extensively for use in high-temperature thermoelectric applications. Specifically, lanthanum and praseodymium-based compounds with the Th3P4 structure type have demonstrated dimensionless thermoelectric figures of merit (zT) up to 1.7 at 1200 K. Scandium, while not part of the lanthanide series, is considered a RE element due to its chemical similarity. However, little is known about the thermoelectric properties of the tellurides of scandium. Here, we synthesized scandium sesquitelluride (Sc2Te3) using a mechanochemical approach and formed sintered compacts through spark plasma sintering (SPS). Temperature-dependent thermoelectric properties were measured from 300–1100 K. Sc2Te3 exhibited a peak zT = 0.3 over the broad range of 500–750 K due to an appreciable power factor and low-lattice thermal conductivity in the mid-temperature range.
Highlights
Thermoelectric materials are used as solid-state energy conversion devices to transform thermal energy into electrical power
The thermoelectric materials integrated into the Radioisotope thermoelectric generators (RTGs) have demonstrated long-term reliability, with the Voyager 1 and 2 missions continuously operating for over 40 years [2,3,4,5]
The powder was compacted in a 12.7-mm graphite die using spark plasma sintering (SPS) at a temperature above 1450 K and a pressure of 80 MPa for 30 min under vacuum
Summary
Thermoelectric materials are used as solid-state energy conversion devices to transform thermal energy into electrical power. The dimensionless thermoelectric figure of merit is a measure of a material’s conversion efficiency and is defined as zT = SρκT , where S is the Seebeck coefficient, ρ is the electrical resistivity, κ is the thermal conductivity, and T is the absolute temperature. Good thermoelectric materials will have a high Seebeck coefficient, low electrical resistivity, and low thermal conductivity. One limitation of these devices is that they exhibit modest thermal-to-electrical system level conversion efficiencies of approximately 6.5% at beginning-of-life, due to the average zT values of the heritage materials being less than 1 over their operating temperature range [1,4]. Identification of materials with high zT values is critical for increasing the efficiencies of RTGs, which would enable greater specific power for future missions
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