Reaction Sintering of Ca3Co4O9 with BiCuSeO Nanosheets for High-Temperature Thermoelectric Composites

Ceramic composites composed of oxide materials have been synthesized by reaction sintering of Ca3Co4O9 with BiCuSeO nanosheets. In situ x-ray diffraction and thermogravimetric analyses of the compound powders were conducted to understand the phase transformations during heating up to 1173 K. Further thermogravimetric analyses investigated the thermal stability of the composites and the completion of reaction sintering. The microstructure of the formed phases after reaction sintering and the composition of the composites were investigated for varying mixtures. Depending on the amount of BiCuSeO used, the phases present and their composition differed, having a significant impact on the thermoelectric properties. The increase of the electrical conductivity at a simultaneously high Seebeck coefficient resulted in a large power factor of 5.4 $$\mu $$ μ W cm−1 K−2, more than twice that of pristine Ca3Co4O9.

High Seebeck coefficient in PVD-WS2 film with grain size enlargement

A high Seebeck coefficient of 1.17 × 103 μV/K was achieved using an on-chip thermoelectric device for a WS2 atomic-layer film, which was synthesized by ultra-high vacuum RF-magnetron sputtering as a function of sputtering power. A layered structure in parallel to SiO2/Si substrate was confirmed from the transmission electron microscopy and X-ray diffraction spectra. The grain size and peak intensities of the Raman spectra increase with a decrease in the sputtering power. Accordingly, the resistivity and activation energy also increase. This WS2 film can be used in thermoelectric generators, such as energy harvesters in LSIs and wearable devices.

Achieving Ultrahigh Power Factor In n-type Ag2Se Thin Films By Carrier Engineering

Ag2Se is a promising n-type material which has been proposed for thermoelectric (TE) application. Achieving high TE power factor for Ag2Se thin film to use in micro and wearable electronic systems has recently attracted great attention. In present work, Ag2Se thin films were prepared via a simple co-evaporation method, which provides an effective way for adjusting its composition. By selective modification of Ag content, the carrier concentration is optimized, leading to a PF of 6.27 μWcm-1K-2. Furthermore, the carrier mobility increased while carrier concentration is maintained after performing an annealing process, thus contributes to relatively high Seebeck coefficient and decent electrical conductivity for Ag2.05Se film annealed at 423 K. As a result, a record-high power factor of 20.51 μWcm-1K-2 at 393 K is achieved, which is the best result of the Ag2Se thin film prepared by evaporation method. This work has opened the way for environmentally friendly room-temperature thermoelectricity.

DFT study of structural, elastic, electronic, magnetic, thermal and transport properties of new multifunctional NiVSn half-Heusler for spintronic and thermoelectric applications

In this work, the first-principles density functional calculations of the structural, elastic, electronic, magnetic, thermal and thermoelectric properties of NiVSn half-Heusler compound are carried out. The exchange and correlation potential are treated by using Generalized Gradient approximation of Perdew, Burke and Ernzerhof (GGA-PBE), GGA plus Tran–Blaha-modified Becke–Johnson (mBJ-GGA) approach and mBJ-GGA+U where U is the Hubbard on-site Coulomb interaction correction (mBJ-GGA+U). Structural calculations revealed that NiVSn is stable in type 1 structure ferromagnetic state. Elastic properties show that our compound is mechanically stable, ductile and anisotropic. The results of the band structures and density of states display a half metallic behavior of NiVSn with an indirect bandgap of 0.476, 0.508 and 0.845 eV by using GGA-PBE, mBJ-GGA, and mBJ-GGA+U, respectively. The total magnetic moment calculated is integer of 1 [Formula: see text]B confirming a half metallic behavior of NiVSn and follows the well-known Slater–Pauling rule ([Formula: see text]); therefore, the studied compound is suitable for application in spintronic fields. The thermodynamic properties such as bulk modulus, the heat capacity, the Debye temperature, and the thermal expansion coefficient are investigated using quasi-harmonic Debye model (QHDM). The thermal results show that NiVSn can be applied in extreme temperature and pressure conditions. The thermoelectric properties are studied employing the BoltzTrap code. The calculated transport properties are very interesting for the spin-down channel with high electrical conductivity, high Seebeck coefficient, and figure of merit value approaching unity. As a result, the half-Heusler alloy NiVSn is a promoter for conventional thermoelectric materials.