Papers by Keyword: Thermoelectric Performance

Abstract: Thermoelectric materials are valued for their ability to convert waste heat into electrical energy. Antimonene nanosheets (AnNS) have recently emerged as a promising thermoelectric material due to their unique two-dimensional structure. However, developing efficient and scalable methods for preparing AnNS-based thermoelectric composites with improved performance remains challenging. In this study, we developed an efficient and environmentally friendly method for preparing antimonene nanosheet (AnNS)/graphene platelets (GNPs) composites using ultrasonic dispersion in an ethanol-based system, followed by thin film fabrication via cold-pressing. Atomic Force Microscopy (AFM) was used to characterize the microstructure and thickness of the nanosheets, while Scanning Electron Microscopy (SEM) images revealed the contact structures at different GNP concentrations. The characterization of the thermoelectric composites involved techniques such as X-ray diffraction (XRD) and Raman spectroscopy. The thermoelectric (TE) performance of the composites was systematically evaluated across different GNP volume fractions. Composites containing 1 vol% GNPs exhibited the highest electrical conductivity, measured at 2158.22 ± 25.5 S/cm, along with a Seebeck coefficient of 27.17 ± 0.15 µV/K, yielding a power factor of 159.34 ± 5.6 µW/m·K². When these composite films were integrated into a thermoelectric generator (TEG) and exposed to a human body temperature gradient of 11 °C, they produced a continuous voltage of 43.62 mV and a current of 0.21925 µA, yielding an output power of 9.56 nW. Additionally, the corrosion resistance of the composites was assessed, revealing that the 1 vol% GNPs composite exhibited superior performance compared to other compositions.

Abstract: Thermoelectric materials can directly convert thermal energy into electrical energy, realizing the recovery of waste heat. Bismuth Telluride (Bi-Te) is considered as a perfect candidate thermoelectric material which has great potential in the field of refrigeration and temperature sensor. However, in the field of intelligent wearable devices and integrated circuits, traditional Bi-Te block material is difficult to be directly used due to its poor flexibility. In this paper, a series of Bi-Te thin films were prepared by a self-designed high-temperature thermal shock equipment. This equipment can heat up the reduced graphene oxide strip to 1750 K in 20 ms, which features both high heating rate (8.2 × 10⁴ K/s) and cooling rate (1.5 × 10⁴ K/s). Thermoelectric films on different substrates were prepared via high-temperature thermal shock. Through regulating the temperature of evaporation source, the particle size and composition of Bi-Te thin films can be precisely modulated, thus optimizing the Seebeck coefficient of the films. The Seebeck coefficient of copper foil (Cu_f)-based Bi-Te film can reach 345.41 μV/K, which was prepared by thermal-shocking the Bi-Te powders for 30 s at 900°C.

Abstract: CaMnO₃ (CMO) thermoelectric material is large Seebeck coefficient but high electrical resistivity. To reduce electrical resistivity by adding carbon nanotubes (CNTs) in CMO material and may be decreased Seebeck coefficient. In this work, we simulated electronic structure of CMO and CNTs-added CMO by DV-Xα method to investigation of power factor and enhance the thermoelectric performance. The Seebeck coefficient and electrical resistivity were calculated by Maxwell-Boltzmann distribution and Mott’s law to investigate power factor. The DV-Xa calculated show the energy level and density of state (DOS) of CMO and CNTs-added CMO demonstrated that the energy gap reduces from 3.33 eV to 0.19 eV affect to enhance the power factor of CMO with Seebeck coefficient and electrical resistivity are decreases. The power factor of CNTs-added CMO was increased with increasing CNTs content.

Abstract: Thermoelectric (TE) phenomenon of a helical generator is numerically analyzed by using the finite-volume method in combination with a three-dimensional finite-element (FE) model. The distributions of temperature and current density are significantly influenced by the generator dimension. The output power of helical generator is also affected by the geometric parameter, such as the helical pitch. The output power and conversion efficiency of helical generator are better than those of straight generator where all the TE elements aligned in a straight line. The helical geometry has a satisfactory potential to be a good TE generator.

Abstract: In the present study, the glass microsphere dispersed Bi-Sb thermoelectric materials have been fabricated through mechanical alloying followed by pressureless sintering. The phase composition and the microstructure were investigated by X-ray diffraction (XRD) and scanning electron microscopy (SEM) analysis. Electrical conductivity, Seebeck coefficient and thermal conductivity were measured in the temperature range of 77~300 K. The ZT values were calculated according to the measurement results. The results showed that the electrical conductivity, Seebeck coefficient and thermal conductivity decreased by adding glass microsphere into Bi-Sb thermoelectric materials. However, the optimum ZT value of 0.24 was obtained at 260 K, which was increased 10% than that of the Bi-Sb matrix. So it is confirmed that the thermoelectric performance of Bi-Sb-based materials can be improved by adding moderate glass microspheres.

Abstract: A series of n-type BiTeSe/ZnAlO composites were prepared by zone melting method. Thermoelectric properties, including the electrical conductivity σ, Seebeck coefficient α and thermal conductivity κ, were measured in the temperature range of 300-550K. Results show that the electrical properties have been slightly lowered due to the reduced carrier concentration by ZnAlO addition. However, the low-temperature-shifted peak α, resulting from the prematurely happened intrinsic excitation, have shifted peak ZT to lower temperatures. As a result, the ZT values at 300 K were significantly enhanced for BiTeSe/ZnAlO composites compared to that of BiTeSe, making more attractive for cooling applications at ambient temperature.

Abstract: The layered cobalt oxides as thermoelectric (TE) materials are introduced in detail on their developments, representative systems, some theories, unsolved problems and approaches for improving performances. TE performances of the layered cobalt oxides are discussed from structures, doped situations, processes and the dimensionless figure of merit. In contrast with other TE materials, the layered cobalt oxides show many promising applications. The theory of Seebeck coefficient and hopping conduction mechanism in the layered cobalt oxides are discussed. Heike formula explains that Seebeck coefficient origins from electronic spin states and proportions of different value states of Co ion. An unbalance of the spin and orbital degrees of freedom between Co3+ and Co4+ sites results in the large Seebeck coefficient. On the basis of the Boltzmann transport equation, Seebeck coefficient is decided by energy band structures. High state density near Fermi Energy band is responsible for the coexistence of large Seebeck coefficient and high electrical conductivity. Hopping conduction mechanism found in experiments is a main transport way of charge carriers at high temperature for the layered cobalt oxides. Through different materials systems and theories analysis, unsolved problems and new approaches for improving TE performances are put forward.