Fabrication of Seebeck coefficient measurement system and thermoelectric properties in Sn1-xAgxTe compounds

Abstract

Pb-based materials, which are superior for thermoelectric performance, environmentally have toxicity. Thus the materials should be alternated by non-toxic materials. Tin telluride (SnTe) is isostructural with PbTe and PbSe which are rock salt structure. In addition, SnTe is similar to the electronic band structure (two valence band system) with PbTe and PbSe. Thus, SnTe, which is overcome by low Seebeck coefficient and by large thermal conductivity, can be expected by good thermoelectric material. Thus, Ag-included poly crystals Sn1-xAgxTe (x=0.1, 0.2, 0.3, and 0.4) were prepared by box furnace and by hot press to confirm thermoelectric performance of the samples. By accident, we noticed difference that XRD patterns of Sn1-xAgxTe are changed from two phases (SnTe, AgTe) to mixed phase (SnTe/AgTe) before hot pressing and after. In addition, electrical conductivity of samples is maintained until high temperature. The power factor of sample to include silver(x=0.1) has maximum value (1.1 mW/mK2) at 673K. However, SnTe has higher power factor than Ag-included SnTe. Nevertheless, we can carefully expect that sample to include mixed phase obtain high electrical conductivity. Exceptionally, we developed the measurement of the thermoelectric power in the temperature range from 2K to 300K. By using two heaters, two thermometer, chip resistors, et al, measurement equipment is fabricated exactly. In addition, high density data is obtained by two heaters that are operated by turn. The system is controlled by LabVIEW software. In order to demonstrate this system, reference data of Pt wire and Ca10Nax(Pt3As8)(Fe2As2)5 superconductor were calibrated by developed equipment. Therefore we demonstrated the equipment with superior performance through confirming calculated data. ⓒ 2015 DGIST