Thermoelectric materials are a highly promising category of energy conversion materials. In this paper, we present a multitude of approaches to enhance the efficacy of these materials. The review begins with an introduction to the fundamental concept of the thermoelectric figure of merit (ZT), a key parameter for assessing the performance of thermoelectric materials, as well as theories of electrical and thermal transport, which lay the groundwork for understanding and improving the performance of thermoelectric materials. Subsequently, this paper delves into several typical optimization strategies, including the enhancement of material performance through low-dimensionalization and quantum confinement effects, with detailed discussions on two-dimensional, one-dimensional, and zero-dimensional materials. The role of point defect engineering in modulating material properties and the significance of nano-composite materials in enhancing thermoelectric performance are also explored. Band engineering, an effective optimization technique, offers multiple possibilities for enhancing thermoelectric performance through the adjustment of carrier effective mass, utilization of resonance states, band degeneracy, band convergence, and bandgap tuning. Additionally, the application of phonon engineering in reducing thermal conductivity and improving thermoelectric conversion efficiency is highlighted. Discussions on special structures such as textures, single crystals, core–shell structures, and porous structures, as well as symmetry control strategies, highlight the importance of microstructural control in optimizing thermal conductivity. Consequently, the review explores the significance of the synergistic effects of different strategies, noting that an integrated application of these strategies can maximize the performance of thermoelectric materials. The use of materials genomics and machine learning in screening highly potential thermoelectric materials is also highlighted. Finally, the paper addresses the challenges and developments related to the stability, scalability, sustainability, and integration of thermoelectric materials with other systems. Overall, this article summarizes a series of optimization strategies for thermoelectric materials, providing valuable references and inspiration for researchers in the field, with the aim of further advancing the science of thermoelectric materials.

Transition metal nitride (TMN) films with excellent hardness and lubricating performance are versatile low dimension materials, which are widely used in various fields including industries, transportation, aerospace, and so on. This paper introduces one film design strategy and provides a review of the mechanisms for strengthening and lubricating nitride films. The design strategy refers to two aspects which determine the structures, the performance, the components, and the chemical constitutions of nitride films The strengthening mechanisms of nitride films are then illuminated in detail, including the solid solution effect, the grain size effect, the secondary phase effect, the stress or stress field effect, the template effect, and the valence electron concentration effect. Five lubricating mechanisms are next summarized, including the easy-shear nature, the tribo-chemical reactions, the lubricious fluorides, the textured contact surface, and the synergistic effect. This paper aims to give a comprehensive introduction for understanding the mechanisms of strengthening and lubrication of nitride films for students and researchers, as well as to understand the current research progress in nitride films for exploring research gaps.

In this study, Bi_2−xTa_xO₂Se (x = 0, 0.02, 0.04, 0.06, and 0.08) ceramics were prepared using a synthesis method combining high-energy ball milling and cold pressing. Furthermore, the effects of tantalum (Ta) doping on the microstructure and thermoelectric properties of Bi₂O₂Se were systematically investigated. The results indicate that Ta doping effectively improves the carrier concentration and mobility, thus increasing the electrical conductivity from 8.75 S cm⁻¹ to 39.03 S cm⁻¹ at 323 K. Consequently, the power factor is improved, reaching a maximum value of 124 μW m⁻¹ K⁻² for the Bi_1.92Ta_0.08O₂Se sample at 773 K. Moreover, the thermal conductivity of Bi_1.96Ta_0.04O₂Se is reduced to 0.50 Wm⁻¹ K⁻¹. Finally, the maximum dimensionless figure of merit (ZT) value of the Bi_1.94Ta_0.06O₂Se sample reached 0.18, which was 64% higher than that of Bi₂O₂Se (0.11). These results indicate that Ta doping and high-energy ball milling can optimize the electrical and thermal properties and thus improve the thermoelectric properties of ceramics.

Photocatalysis technology, as an efficient and safe environmentally friendly purification technique, has garnered significant attention and interest. Traditional TiO₂ photocatalytic materials still face limitations in practical applications, hindering their widespread adoption. The research prepared TiO₂/Cu films with different Cu contents using a magnetron sputtering multi-target co-deposition technique. The incorporation of Cu significantly enhances the antibacterial properties and visible light response of the films. The effects of different Cu contents on the microstructure, surface morphology, wettability, antibacterial properties, and visible light response of the films were investigated using an X-ray diffractometer, X-ray photoelectron spectrometer, field emission scanning electron microscope, confocal laser scanning microscope, Ultraviolet–visible spectrophotometer, and contact angle goniometer. The results showed that the prepared TiO₂/Cu films were mainly composed of the rutile TiO₂ phase and face-center cubic Cu phase. The introduction of Cu affected the crystal orientation of TiO₂ and refined the grain size of the films. With the increase in Cu content, the surface roughness of the films first decreased and then increased. The water contact angle of the films first increased and then decreased, and the film exhibited optimal hydrophobicity when the Cu target power was 10 W. The TiO₂/Cu films showed good antibacterial properties against Escherichia coli and Staphylococcus aureus. The introduction of Cu shifted the absorption edge of the films to the red region, significantly narrowed the band gap width to 2.5 eV, and broadened the light response range of the films to the visible light region.

Cu₃SbSe₄ is a potential p-type thermoelectric material, distinguished by its earth-abundant, inexpensive, innocuous, and environmentally friendly components. Nonetheless, the thermoelectric performance is poor and remains subpar. Herein, the electrical and thermal transport properties of Cu₃SbSe₄ were synergistically optimized by S alloying. Firstly, S alloying widened the band gap, effectively alleviating the bipolar effect. Additionally, the substitution of S in the lattice significantly increased the carrier effective mass, leading to a large Seebeck coefficient of ~730 μVK⁻¹. Moreover, S alloying yielded point defect and Umklapp scattering to significantly depress the lattice thermal conductivity, and thus brought about an ultralow κ_lat ~0.50 Wm⁻¹K⁻¹ at 673 K in the solid solution. Consequently, multiple effects induced by S alloying enhanced the thermoelectric performance of the Cu₃SbSe₄-Cu₃SbS₄ solid solution, resulting in a maximum ZT value of ~0.72 at 673 K for the Cu₃SbSe_2.8S_1.2 sample, which was ~44% higher than that of pristine Cu₃SbSe₄. This work offers direction on improving the comprehensive TE in solid solutions via elemental alloying.