Development of a Measurement System for the Figure of Merit in the High-Temperature Region

• Published in: Journal of electronic materials 2013-07, Vol.42 (7), p.1840-1845
• Main Authors: Iwasaki, H., Yamamoto, T., Kim, H., Nakamoto, G.
• Format: Article
• Language: English
• Subjects: Characterization and Evaluation of Materials; Chemistry and Materials Science; Condensed matter: electronic structure, electrical, magnetic, and optical properties; Condensed matter: structure, mechanical and thermal properties; Conductivity phenomena in semiconductors and insulators; Electric properties; Electronic structure and electrical properties of surfaces, interfaces, thin films and low-dimensional structures; Electronic transport in condensed matter; Electronic transport phenomena in thin films and low-dimensional structures; Electronics and Microelectronics; Exact sciences and technology; Heat conductivity; High temperature superconductors; Instrumentation; Materials Science; Measurement techniques; Optical and Electronic Materials; Physical radiation effects, radiation damage; Physics; Solid State Physics; Structure of solids and liquids; crystallography; Thermoelectric and thermomagnetic effects; Thermoelectric effects
• ISSN: 0361-5235; 1543-186X
• DOI: 10.1007/s11664-012-2448-0

New equipment has been developed for evaluating the figure of merit, ZT , on the basis of the Harman method in the temperature range between room temperature and 650 K. In this temperature range, the sample holder in the vacuum chamber has a different construction as compared with the sample holder constructed for the temperature range below room temperature. Several issues that need to be considered, such as compensation for the thermal radiation effect, suppression of heat leakage from the lead wires, and the setup method for the lead wires on the sample, are examined in the considered temperature region. Evaluations of ZT are successfully made for typical thermoelectric materials, (Bi,Sb) 2 Te 3 and CeFe 3 CoSb 12 . We then demonstrate that the influence of thermal radiation between the high- and low-temperature edges of the sample induced by the Peltier effect on the estimated value of ZT is negligible at around 600 K. Furthermore, the change in the thermoelectric properties due to repetition of the thermal cycle is studied, and a typical hysteresis behavior is observed in the considered thermoelectric materials. It is revealed that heating the sample to a high temperature causes a change in its thermoelectric properties, which one must take into account for practical applications of thermoelectric materials.