Thermoelectric materials are fascinating as a solution to boost cost-effective energy harvesting due to their ability to convert heat directly into electricity and vice versa [1]. The conversion efficiency of thermoelectric material is governed by the dimensionless figure of merit (ZT) and is defined as ZT = S2T/ρκtotal, where S is the Seebeck coefficient, ρ is the electrical resistivity, and κtotal is the total thermal conductivity. The κtotal represents the sum of lattice thermal conductivity (κL) and electronic thermal conductivity (κe), and T is the absolute temperature. The strong charge carrier coupling between S, ρ, and κe poses a barrier to increasing the ZT values of a TE material. Nevertheless, κL is independent of the charge carriers and can be amicably reduced through effective strategies. Among the various TE materials explored so far, Co4Sb12-based filled skutterudites are getting considerable attention for their potential thermoelectric applications in the mid-temperature range applications (500−750 K) [1]. So far, the highest ZT is achieved only in multiple rare-earth filled skutterudites (1.8 for n-type and 1.6 for p-type). Nevertheless, the multiple filling may make the TE material system more complex and non-reproducible for practical applications. In addition, the availability of RE elements is scarce nowadays. Single rare-earth-filled skutterudites still show lower ZT owing to their higher thermal conductivity and moderate power factor. Enhancing the Seebeck coefficient and reducing κL for the single-filled skutterudites are practical approaches that may improve their TE performance. Strategies such as carrier concentration engineering and band structure modification have been identified are practical approaches for ZT enhancement. A thermoelectric module is a complex set of different materials which needs to be engineered in a highly sophisticated manner to provide a long-term flawless and constant performance concerning thermoelectric efficiency, which in turn directly depends on a chemically and metallurgically unaltered materials’ constitution. In designing TE devices, finding a proper joint material to form leg-electrode interfaces is essential. In the present work, single-filled skutterudites have been processed using the powder metallurgy route to avoid the multiple rare-earth elements filling and obtain high-efficient skutterudites[2]. It is observed that Ni-doping at the Co site enhances the TE properties of single-filled skutterudites through improved charge carrier concentration at the Fermi level and enhanced phonon scattering by creating Ni-rich grain boundaries[3]. The strategy to enhance the thermoelectric properties of both n-type and p-type skutterudites through band engineering and nanostructuring was explored. The carrier filtering approach by ex-situ dispersion of rare-earth oxide nanoparticles in skutterudite matrix was utilized for ZT enhancement. Further, a thermoelectric prototype using indigenous n-type and p-type skutterudite legs with thermally and mechanically stable electrode/thermoelectric joints was designed, fabricated, and demonstrated[4].
[1] V. Trivedi, M. Battabyal, P. Balasubramanian, G.M. Muralikrishna, P.K. Jain, R. Gopalan, Microstructure and doping effect on the enhancement of the thermoelectric properties of Ni doped Dy filled CoSb3 skutterudites, Sustain. Energy Fuels. 2 (2018) 2687–2697. https://doi.org/10.1039/c8se00395e.
[2] V. Trivedi, M. Battabyal, S. Perumal, A. Chauhan, D.K. Satapathy, B.S. Murty, R. Gopalan, Effect of Refractory Tantalum Metal Filling on the Microstructure and Thermoelectric Properties of Co4Sb12Skutterudites, ACS Omega. 6 (2021) 3900–3909. https://doi.org/10.1021/acsomega.0c05740.
[3] V. Trivedi, M. Tiadi, B.S. Murty, D.K. Satapathy, M. Battabyal, R. Gopalan, Giant Thermoelectric Efficiency of Single-Filled Skutterudite Nanocomposites: Role of Interface Carrier Filtering, ACS Appl. Mater. Interfaces. (2022). https://doi.org/10.1021/acsami.2c13747.
[4] V. Trivedi, M. Battabyal, B.S. Murty, R. Gopalan, Interfacial thermoelectric and mechanical properties of indigenously prepared Ni–Cr–Cu/Co4Sb12 skutterudite thermoelectric joints, Ceram. Int. 48 (2022) 29175–29182. https://doi.org/10.1016/j.ceramint.2022.05.131.