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Nanostructured Ni-substituted Co1−xNixSb3 (0 ≤ x ≤ 0.08) samples were synthesized using a hydrothermal method. X-ray diffraction analysis confirmed the phase purity of the samples, and a secondary phase was observed in samples with higher Ni substitution ratios (x ≥ 0.06). SEM and TEM images reveal the spherical morphology of the samples with monodispersed particles. Different modes of optic phonon vibrations were observed in Raman spectra, and the intensity of the peaks increased with Ni content and slightly decreased in samples with x values ≥0.06. The electrical resistivity of the samples decreased with Ni content up to an x value of 0.06 and slightly increased in Co0.92Ni0.08Sb3 due to secondary phase formation. The positive Seebeck coefficient values of pure CoSb3 confirm that holes were the majority carriers, whereas the negative Seebeck coefficients of Co1−xNixSb3 samples reveal that Ni substitution enhanced electron concentration in the sample. Co0.96Ni0.04Sb3 exhibited a higher power factor compared with other samples due to its low resistivity. Ni substitution in CoSb3 effectively reduced lattice thermal conductivity (κL) as Co0.96Ni0.04Sb3 showed a lower κL of 2.0 W m−1 K−1 than that of the pure sample due to nanostructuring and the rattling effect of Ni. As a result, a figure of merit of 1.72 was achieved at 553 K for the Co0.96Ni0.04Sb3 sample. [ABSTRACT FROM AUTHOR]

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]

Earth-adequate quaternary chalcogenides like Cu2NiSnS4 with more complex crystal structures can become non-toxic and cost-effective thermoelectric (TE) materials. TE materials, by employing the energy filtering effect through appropriate energy bandgap, have enhanced their TE efficiency. The composition of CuO in Cu2NiSnS4 matrix has enhanced the Seebeck coefficient (S) and declined the thermal conductivity (κ) simultaneously, due to the decrement of carrier concentration (n), by increasing the wt% of CuO in the composites. The highest power factor of 270.88 μW m−1 K−2 at 573 K is recorded for 30 wt% composites. The 30 wt% composite material thermal conductivity exhibited a low value of 0.442 W m−1 K−1 through stronger phonon scattering at the interface boundaries formed between the Cu2NiSnS4 matrix and CuO compositions. A maximum zT of 0.35 for the Cu2NiSnS4/30 wt% CuO composite was obtained, 75% larger than that of the Cu2NiSnS4 matrix at 573 K. This strategy of introducing metal oxides into the metal sulphide matrix for obtaining efficient TE performance could be extended to other eco-friendly quaternary chalcogenides. [ABSTRACT FROM AUTHOR]

This study details the successful creation of a nanocomposite consisting of reduced graphene oxide (rGO) and Yb2O3 using a hydrothermal-assisted simple solution method. The research underscores the significance of this rGO: Yb2O3 composite material, which has emerged as a focal point of interest. The comprehensive analysis of the composite's structural features, as revealed by various techniques, offers vital insights into its distinctive properties. These insights hold profound implications for potential applications, especially in the field of advanced materials. The structural characterization techniques not only enhance our understanding of the composite's crystal structure, molecular vibrations, elemental composition, and surface chemistry but also highlight its potential as a superior material for various scientific and technological endeavors. Furthermore, this study emphasizes the importance of research and development efforts dedicated to rGO: Yb2O3 composite materials, particularly in the context of supercapacitor applications. Morphological examinations confirm the uniform distribution of Yb2O3 nanoparticles on both sides of the rGO sheets, with sizes below 50 nm. Notably, the nanocomposite exhibits significantly enhanced specific capacitance (1382.72 Fg−1 at 5 mVs−1) compared to pristine Yb2O3 nanoparticles (753.27 Fg−1 at 5 mVs−1). This improvement can be attributed to the synergistic interaction between rGO and Yb2O3, which enhances the charge storage capacity. Electrochemical characterization reveals dominant pseudo-capacitance behavior typical of batteries, making the nanocomposite a promising candidate for energy storage applications. In summary, this study illuminates the potential of graphene-based nanocomposites as high-performance energy storage materials and offers valuable insights for future research endeavors, including optimizing synthesis parameters and evaluating long-term stability. The rGO: Yb2O3 nanocomposite exhibits tremendous promise for advanced energy storage systems. [ABSTRACT FROM AUTHOR]

Recently, thermoelectric (TE) materials have seized great attention for their role in clean energy conversion applications. Cu2S are p-type super-ionic conductors featuring a narrow band gap of 1.7 eV while exhibiting outstanding thermoelectric characteristics. The Cu2S matrix and the CuO nanoinclusions were successfully synthesized via solvothermal and hydrothermal routes, respectively. The morphological observations made through scanning and transmission electron microscope ensured the homogeneous distribution of CuO nanoinclusions in the Cu2S matrix, hence, the formation of standard Cu2S/CuO composites. In this work, we have introduced a "combined strategy" to boost the figure of merit (zT). The Seebeck coefficient reached the maximum of 271.86 μVK−1 at 573 K for the 20 wt% CuO sample (a 71.45% gain when compared to the pure Cu2S) owing to the filtration of low-energy carriers at the CuO potential barriers (2.5 eV). The Cu2S/20 wt% CuO sample achieved the minimum thermal conductivity values. At 573 K, We recorded a vast power factor value of 952.66 μWm−1 K−2 (32.23% gain) for the Cu2S/15 wt% CuO sample. These values are vastly higher than previously reported for the copper sulfides-based TE materials. Consequently, an optimised zT value of 0.44 (214.29% gain) was accomplished for the Cu2S/15 wt% CuO sample at 573 K. The strategy presented in our study can also be extended to other TE materials, especially for the promising copper chalcogenides to improve their zT values. [ABSTRACT FROM AUTHOR]