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Oxygen stoichiometry plays a vital role in determining the physical properties of transition metal oxides (TMOs) and their suitability for high-temperature thermoelectric applications. In the present study, oxygen-deficient BaBixCo1–xO3–δ (0 ≤ x ≤ 0.2) perovskite samples were synthesized using the sol-gel method. Structural analysis revealed the formation of oxygen-deficient phases with hexagonal structures. Morphological analysis showed significant changes in the size and interlayer growth of these phases with various levels of bismuth (Bi) substitution. The high thermal stability of the samples was confirmed by TGA. The binding state and composition of the samples were analysed by XPS. Thermoelectric studies were performed, and the results indicated that the electrical resistivity (ρ) decreased with temperature, indicating the semiconducting behavior of the samples. The Seebeck coefficient (S) increased for the samples with higher Bi content due to energy filtering effect. The sample with x value of 0.1 shows a high-power factor of 0.001 µWK− 2m– 1 at 600 K compared to other samples. The experimental findings demonstrated that the oxygen deficient BaBixCo1–xO3 – δ perovskite material exhibited high thermoelectric performance compared to the sample with mixed phase. Furthermore, Bi substitution was found to be a promising strategy for enhancing the thermoelectric performance, with specific compositions showing great potential for high-temperature thermoelectric applications. [ABSTRACT FROM AUTHOR]

Nanostructured SnSe1−xTex (0 ＜ x ＜ 0.2) was prepared by the planetary ball milling method. The prepared materials were studied by various analytical techniques. XRD analysis shows the pure phase of SnSe when x≤ 0.1 and the secondary phase of SnTe was observed when x≥ 0.1, possibly due to the low solid solubility limit of Te in SnSe. FESEM images revealed that the grain sizes of all the samples were in the range of 100 to 500 nm. TEM images showed the grain structures, sizes and grain boundaries of the samples. XPS analysis confirmed the incorporation of Te in SnSe1−xTex and the binding states of the elements in the samples. The samples were made into pellets and sintered at high temperature. The electrical resistivity of the SnSe1−xTex pellets decreased by up to two orders of magnitude as the x value increased in the samples. Concomitantly, the Seebeck coefficient of the SnSe1−xTex samples decreased drastically as the x value increased in the samples. A power factor (PF) of 102.8 μW K−2 m−1 was obtained for the SnSe0.9Te0.1 sample at 550 K, which is higher than the reported values for SnSe and SnSe1−xTex. When substituting Se with Te, the band structure of SnSe changes, which significantly enhances the thermoelectric PF of SnSe1−xTex for x∼ 0.1. The PF decreased when the x value was increased further (x≥ 0.1), possibly due to the precipitation of the SnTe phase. These experimental results demonstrate that the addition of a reasonable amount of Te is a promising approach for improving the thermoelectric properties of SnSe. [ABSTRACT FROM AUTHOR]

Bi x ZnCo 2- x O 4 (0 ≤ x ≤ 0.2) nanoparticles with different x values have been prepared by the sol-gel method; the structural, morphological, thermal and thermoelectric properties of the prepared nanomaterials are investigated. XRD analysis confirms that Bi is completely dissolved in the ZnCo 2 O 4 lattice till the x values of ≤0.1 and the secondary phase of Bi 2 O 3 is formed at higher x value ( x > 0.1). The synthesized nanomaterials are densified and the thermoelectric properties are studied as a function of temperature. The electrical resistivity of the Bi x ZnCo 2- x O 4 decreased with x value and it fell to 4 × 10 -2 Ω m for the sample with x value ≤ 0.1. The Seebeck coefficient value increased with the increase of Bi substitution till the x value of 0.1 and decreased for the sample with higher Bi content ( x ≤ 0.2) as the resistivity of the sample increased due to secondary phase formation. With the optimum Seebeck coefficient and electrical resistivity, Bi 0.1 ZnCo 1.9 O 4 shows the high-power factor ( α 2 σ 550 K ) of 2.3 μW K -2 m -1 and figure of merit of 9.5 × 10 -4 at 668 K respectively, compared with other samples. The experimental results reveal that Bi substitution at the Co site is a promising approach to improve the thermoelectric properties of ZnCo 2 O 4 ., Competing Interests: There is no conflict of interest to declare., (This journal is © The Royal Society of Chemistry.)