Improving thermoelectric performance of indium thiospinel by Se- and Te-substitution

• Published in: Journal of materials chemistry. C, Materials for optical and electronic devices Materials for optical and electronic devices, 2021-03, Vol.9 (11), p.48-419
• Main Authors: Wy ga, Pawe, Grimm, Sven, Garbe, Valentin, Zuñiga-Puelles, Esteban, Himcinschi, Cameliu, Veremchuk, Igor, Leithe-Jasper, Andreas, Gumeniuk, Roman
• Format: Article
• Language: English
• Subjects: Carrier density; Carrier mobility; Current carriers; Electron mass; Electron transport; Electronic structure; Figure of merit; Power factor; Raman spectroscopy; Reduction; Seebeck effect; Substitutes; Tellurium; Thermal conductivity; Thermoelectricity; Transport properties; X ray powder diffraction
• ISSN: 2050-7526; 2050-7534
• DOI: 10.1039/d1tc00291k

A structural and thermoelectric study of the polycrystalline Se- and Te-substituted In 2.67 S 4 thiospinels was performed. The obtained In 2.67 S 4− x Se x (0 ≤ x ≤ 0.5) and In 2.67 S 4− y Te y (0 ≤ y ≤ 0.15) samples were single phase and the solubility limits of Se and Te were not reached. A comprehensive phase analysis based on powder X-ray diffraction and Raman spectroscopy, as well as Rietveld refinements, confirmed that Se/Te-incorporation into the structure of binary β-In 2.67 S 4 ( x = 0) favors the formation of the cubic α-modification for x > 0.15 and y ≥ 0.05. Moreover, both cubic and tetragonal phases were shown to coexist in the In 2.67 S 3.9 Se 0.1 specimen. The Se/Te-for-S substitution strongly influenced electronic transport properties, leading to an increase of the charge carrier concentration and thus, a reduction of the electrical resistivity and Seebeck coefficient. A decrease of charge carrier mobility, observed previously upon the stabilization of the α-phase, was partially counterbalanced by a reduction of effective electron mass, as revealed by the electronic structure calculations. This resulted in the enhancement of the power factor PF > 10 −4 W m −1 K −2 above RT for In 2.67 S 3.9 Se 0.1 and In 2.67 S 3.5 Se 0.5 thiospinels in comparison to pristine In 2.67 S 4 . Combination of such an effect with the decreased thermal conductivity ( i.e. , < 1.5 W m −1 K −1 above RT) led to the improvement of the thermoelectric figure of merit by factor of 2.5 in In 2.67 S 3.5 Se 0.5 . Substitution of S by Se or Te in the In 2.67 S 4 thiospinel was accompanied by an improvement of the charge carrier concentration and a reduction of the effective electron mass, which resulted in the enhancement of the thermoelectric figure of merit ZT .