Thermoelectric properties of cubic Ba-substituted strontium disilicide, Sr1-xBaxSi2, with Ba content above solid solubility limit

• Published in: Intermetallics 2020-12, Vol.127, p.106981, Article 106981
• Main Authors: Singh, Shiva Kumar, Imai, Motoharu
• Format: Article
• Language: English
• Subjects: A. intermetallics (aluminides; B. thermoelectric properties; Barium; Bismuth tellurides; C. powder metallurgy (including sintering and consolidation); Electrical resistivity; Figure of merit; Low temperature; Plasma sintering; Properties (attributes); Seebeck effect; Silicides; Solid solubility; Spark plasma sintering; Substitutes; Sustainable development; Synthesis; Temperature; Thermal conductivity; Thermoelectric materials
• ISSN: 0966-9795; 1879-0216
• DOI: 10.1016/j.intermet.2020.106981

In the interest of the sustainable development of society, it is preferable to construct next-generation thermoelectric devices using materials from earth-abundant elements. In conventional thermoelectric devices for low temperature applications, Bi2Te3-based materials that consists of scarce elements have been used. Cubic strontium disilicide (SrSi2) is a potential thermoelectric material for low temperature applications that consists of earth-abundant elements. To enhance the value of dimensionless thermoelectric figure of merit ZT of cubic SrSi2, partial substitution of Sr atoms with Ba atoms was examined. Cubic Ba-substituted SrSi2, Sr1-xBaxSi2 (x = 0.00, 0.09, and 0.19), was synthesized by spark plasma sintering at 250 MPa and 1023 K, and its thermoelectric properties, such as electrical resistivity ρ, Seebeck coefficient S, and thermal conductivity κ, were measured at temperatures ranging from 10 to 380 K. The sample with Ba content x above the Ba solid solubility limit in cubic SrSi2 (0.13) was successfully synthesized. With increasing x, ρ, and S increase while κ decreases, leading to an increase of ZT with x. ZT exhibits a maximum at a temperature Tmax, which shifts from 313 to 357 K when x increases from 0 to 0.19. The maximum ZT value for cubic Sr0.81Ba0.19Si2 in the present study was calculated to be 0.21 at 357 K. The ZT value obtained is higher than previously reported values for cubic Sr1-xBaxSi2 and cubic Sr1-xCaxSi2. These results demonstrate that cubic SrSi2 has properties suitable for low temperature applications. [Display omitted] •Successful synthesis of Sr1-xBaxSi2 with Ba content x above solid solubility limit.•Reduction of thermal conductivity κ due to partial substitution of Ba for Sr atoms.•Successful enhancement of dimensionless figure of merit by reduction of κ.