Although SrTiO3-based perovskites showed a lot of promise as n-type thermoelectric (TE) materials, they demonstrated a low figure of merit value primarily because of their high lattice thermal conductivity (k l). Researchers found it difficult to reduce k l, as a popular route like nanostructuring did not work well with these perovskites possessing low phonon mean free paths. Here, we put forward a novel strategy of designing high-entropy perovskite (HEP) oxides having five transition metals in the B site to induce more anharmonicity causing enhanced multiphonon scattering in order to decrease k l. Using detailed thermodynamic calculations, we designed and synthesized a highly dense Sr­(Ti0.2Fe0.2Mo0.2Nb0.2Cr0.2)­O3 HEP ceramic. An ultralow thermal conductivity of 0.7 W/mK at 1100 K was achieved in this n-type rare-earth-free HEP oxide TE material. The concept of designing HEPs to achieve ultralow thermal conductivity potentially opens up a new avenue for enhancing TE performance of environmentally benign bulk oxides for high-temperature TE power generation.

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The thermoelectric generator (TEG) is considered as one of the most promising technologies for clean energy generation. But performance optimization with respect to its design and architecture is required for wide-scale commercialization. In this study, we have carried out finite element modeling (FEM) of a SnSe-based thermoelectric generator (TEG) considering electrical contact loss and various heat losses under isothermal and isoflux heat boundary conditions. The conventional Π-architecture comprising both p- and n-legs often results in overall poor performance due to the inferior efficiency of the n-leg TE module compared to its p-counterpart even though SnSe holds high ZT values (≥2). To counter that, we have strategized to design only a p-legged architecture and evaluated its performance in terms of power output and efficiency. Step-by-step optimization of internal and system level parameters for a multiple p-legged as well as traditional p–n-legged TEG has been carried out. Further, Al-based fins have been used to increase the net heat capturing area in the case of the isoflux heat boundary condition. The incorporation of fins facilitates us to redefine an internal parameter called fill fraction (FF) in terms of system level parameters, which leads to easier optimization of the TEG. Keeping in mind the practical application of a TEG in automobile exhaust, simulation of multiple p-legged architecture has resulted in maximum power output of 6.61 and 3.45 W under the isothermal and isoflux heat boundary conditions, respectively. In the FEM considering various thermal and electrical losses under the isothermal heat boundary condition, a maximum efficiency of 4.8% has been obtained in the case of Π-architecture, which is slightly higher than that obtained in the multiple p-legged TEG (3.48%). However, under the isoflux scenario, which is more commonly found in practical waste-heat sources, a maximum efficiency of 17.5% has been achieved for multiple p-legged architecture, which is 14 times higher than that attained for Π-architecture (1.24%). Also, a huge surge (500%) in maximum power output has been observed for the proposed multiple p-legged TEG compared to Π-architecture in our FEM considering various thermal and electrical losses in the isoflux heat source condition. Furthermore, the investigation of thermal and mechanical stability in terms of generated von Mises stress and deformation due to a significant temperature difference has revealed that multiple p-legged architecture is indeed more stable as compared to a Π-architecture TEG under both of the heat boundary conditions.