Search results for "thermoelectric material"
showing 10 items of 72 documents
Thermal conductivity of thermoelectric Al-substituted ZnO thin films
2013
ZnO:Al thin films with a low electrical resistivity were grown by magnetron sputtering on sapphire substrates. The cross-plane thermal conductivity (κ = 4.5 ± 1.3 W/mK) at room temperature is almost one order of magnitude lower than for bulk materials. The thermoelectric figure of merit ZT at elevated temperatures was estimated from in-plane power factor and the cross-plane thermal conductivity at room temperature. It is expected that the thermal conductivity drops with increasing temperature and is lower in-plane than cross-plane. Consequently, the thin film ZT is at least three times higher than for bulk samples at intermediate temperatures. (© 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinh…
Structural Principles and Thermoelectric Properties of Polytypic Group 14 Clathrate-II Frameworks
2013
We have investigated the structural principles and thermoelectric properties of polytypic group 14 clathrate-II frameworks using quantum chemical methods. The experimentally known cubic 3C polytype was found to be the energetically most favorable framework, but the studied hexagonal polytypes (2 H, 4 H, 6 H, 8 H, 10 H) lie energetically close to it. In the case of germanium, the energy difference between the 3C and 6H clathrate-II polytypes is ten times smaller than the difference between the experimentally known 3C-Ge (α-Ge) and 4H-Ge polytypes. The thermoelectric properties of guest-occupied clathrate-II structures were investigated for compositions Na-Rb-Ga-Ge and Ge-As-I. The clathrate-…
Thermal stability and enhanced thermoelectric properties of the tetragonal tungsten bronzes Nb8-xW9+xO47 (0 <x <5)
2017
Thermoelectric materials are believed to play a fundamental role in the energy field over the next years thanks to their ability of directly converting heat into usable electric energy. To increase their integration in the commercial markets, improvements of the efficiencies are needed. At the same time, cheap and non-toxic materials are required along with easily upscalable production cycles. Compounds of the tetragonal tungsten bronze (TTB) series Nb8-xW9+xO47 fulfill all these requirements and are promising materials. Their adaptive structure ensures glass-like values of the thermal conductivity, and the substitution on the cation side allows a controlled manipulation of the electronic p…
Thermoeletric Heusler Compounds
2015
Thermoelectric converters for power generation aim at reducing CO\(_2\) emission via the conversion of a part of the low-grade waste heat generated by engines, industrial furnaces, gas pipes, etc. to electricity. The recovery of waste heat from the exhaust of an automotive engine, in particular, is an attractive, albeit not very efficient way for reduction of fuel consumption. Thermoelectric converters with high overall efficiency convert heat directly into electricity without moving parts and, thus, not only decrease our reliance on fossil fuels but also actively counteract global warming. State-of-the-art converters are simply too inefficient to be economic, partly due to expensive elemen…
Charge carrier concentration optimization of thermoelectric p-type half-Heusler compounds
2015
The carrier concentration in the p-type half-Heusler compound Ti0.3Zr0.35Hf0.35CoSb1−xSnx was optimized, which is a fundamental approach to enhance the performance of thermoelectric materials. The optimum carrier concentration is reached with a substitution level x = 0.15 of Sn, which yields the maximum power factor, 2.69 × 10−3 W m−1 K−2, and the maximum ZT = 0.8. This is an enhancement of about 40% in the power factor and the figure of merit compared to samples with x = 0.2. To achieve low thermal conductivities in half-Heusler compounds, intrinsic phase separation is an important key point. The present work addresses the influence of different preparation procedures on the quality and re…
Topological insulators and thermoelectric materials
2012
Topological insulators (TIs) are a new quantum state of matter which have gapless surface states inside the bulk energy gap. Starting with the discovery of two dimensional TIs, the HgTe-based quantum wells, many new topological materials have been theoretically predicted and experimentally observed. Currently known TI materials can possibly be classified into two families, the HgTe family and the Bi2Se family. The signatures found in the electronic structure of a TI also cause these materials to be excellent thermoelectric materials. On the other hand, excellent thermoelectric materials can be also topologically trivial. Here we present a short introduction to topological insulators and the…
High Electron Mobility and Disorder Induced by Silver Ion Migration Lead to Good Thermoelectric Performance in the Argyrodite Ag8SiSe6
2017
Superionic chalcopyrites have recently attracted interest in their use as potential thermoelectric materials because of extraordinary low thermal conductivities. To overcome long-term stability issues in thermoelectric generators using superionic materials at evaluated temperatures, materials need to be found that show good thermoelectric performance at moderate temperatures. Here, we present the structural and thermoelectric properties of the argyrodite Ag8SiSe6, which exhibits promising thermoelectric performance close to room temperature.
Laser Floating Zone Growth: Overview, Singular Materials, Broad Applications, and Future Perspectives
2021
This article belongs to the Special Issue Laser-Induced Crystallization.
Phonon Bridge Effect in Superlattices of Thermoelectric TiNiSn/HfNiSn With Controlled Interface Intermixing
2020
© 2020 by the authors
La 1−xCaxMnO3 semiconducting nanostructures: morphology and thermoelectric properties
2014
Semiconducting metallic oxides, especially perosvkite materials, are great candidates for thermoelectric applications due to several advantages over traditionally metallic alloys such as low production costs and high chemical stability at high temperatures. Nanostructuration can be the key to develop highly efficient thermoelectric materials. In this work, La 1−xCa x MnO3 perosvkite nanostructures with Ca as a dopant have been synthesized by the hydrothermal method to be used in thermoelectric applications at room temperature. Several heat treatments have been made in all samples, leading to a change in their morphology and thermoelectric properties. The best thermoelectric efficiency has b…