Thermoelectric enhancement in triple-doped strontium titanate with multi-scale microstructure*

Abstract

Strontium titanate (SrTiO3) is a thermoelectric material with large Seebeck coefficient that has potential applications in high-temperature power generators. To simultaneously achieve a low thermal conductivity and high electrical conductivity, polycrystalline SrTiO3 with a multi-scale architecture was designed by the co-doping with lanthanum, cerium, and niobium. High-quality nano-powders were synthesized via a hydrothermal method. Nano-inclusions and a nano/micro-sized second phase precipitated during sintering to form mosaic crystal-like and epitaxial-like structures, which decreased the thermal conductivity. Substituting trivalent Ce and/or La with divalent Sr and substituting pentavalent Nb with tetravalent Ti enhanced the electrical conductivity without decreasing the Seebeck coefficient. By optimizing the dopant type and ratio, a low thermal conductivity of 2.77 W⋅m−1⋅K−1 and high PF of 1.1 mW⋅m−1⋅K−2 at 1000 K were obtained in the sample co-doped with 5-mol% La, 5-mol% Ce, and 5-mol% Nb, which induced a large ZT of 0.38 at 1000 K.

Adaptive genetic algorithm-based design of gamma-graphyne nanoribbon incorporating diamond-shaped segment with high thermoelectric conversion efficiency

“…[5,6] Previously, traditional meth-ods could improve the ZT values of materials by introduction of nanostructures, [7] defect engineering, [8] constructing quantum-well superlattice structures, [9] mixing with cement to make composite materials. [10][11][12] These methods indeed have made some progress in improving the thermoelectric conversion efficiency of materials. Nevertheless, these methods are generally based on random exploration pattern, and the cost of manpower and materials (or computational resources) is enormous during searching for a target structure with ideal thermoelectric performance.…”