Search results for "thermoelectric"
showing 10 items of 188 documents
Thermal conductivity of half-Heusler superlattices
2014
Thin films and superlattices (SLs) of TiNiSn and ZrHfNiSn layers have been grown by dc magnetron sputtering on MgO (100) substrates to reduce the thermal conductivity, aiming for improvement of the thermoelectric figure of merit ZT. The thermal conductivity of 1 Wm−1K−1 was measured by the differential 3ω method for an SL with a periodicity of 8.8 nm. In addition to x-ray diffraction analysis of the SL crystal structure, smooth interfaces were confirmed by scanning/transmission electron microscopy.
Phase separation as a key to a thermoelectric high efficiency
2012
This work elucidates the possible reasons for the outstanding, but never reproduced thermoelectric properties of the doped Ti(0.5)Zr(0.25)Hf(0.25)NiSn Heusler compounds. The structural investigations done via synchrotron X-ray diffraction measurements and scanning electron microscope measurements, which clearly show that the microstructure consists of three temperature stable C1(b) phases with possible semi-coherent interfaces, are presented. The exceptional thermoelectric properties are due to this intrinsic phase separation. It is possible to reproduce the high Figure of Merit values with ZT = 1.2 at 830 K. Furthermore, the influence of doping different elements on the Sn position in this…
Influence of a nano phase segregation on the thermoelectric properties of the p-type doped stannite compound Cu(2+x)Zn(1-x)GeSe4.
2012
Engineering nanostructure in bulk thermoelectric materials has recently been established as an effective approach to scatter phonons, reducing the phonon mean free path, without simultaneously decreasing the electron mean free path for an improvement of the performance of thermoelectric materials. Herein the synthesis, phase stability, and thermoelectric properties of the solid solutions Cu_(2+x)Zn_(1–x)GeSe_4 (x = 0–0.1) are reported. The substitution of Zn^(2+) with Cu^+ introduces holes as charge carriers in the system and results in an enhancement of the thermoelectric efficiency. Nano-sized impurities formed via phase segregation at higher dopant contents have been identified and are l…
INFLUENCE OF THE CHEMICAL POTENTIAL ON THE CARRIER EFFECTIVE MASS IN THE THERMOELECTRIC SOLID SOLUTION Cu2Zn1-xFexGeSe4
2013
In this paper, we describe the synthesis and characterization of the solid solution Cu 2 Zn 1-x Fe x GeSe 4. Electronic transport data have been analyzed using a single parabolic band model and have been compared to Cu 2+x Zn 1-x GeSe 4. The effective mass of these undoped, intrinsically hole conducting materials increases linearly with increasing carrier concentration, showing a non-parabolic transport behavior within the valence band.
Influence of Compensating Defect Formation on the Doping Efficiency and Thermoelectric Properties of Cu2-ySe1–xBrx
2015
The superionic conductor Cu_(2−δ)Se has been shown to be a promising thermoelectric at higher temperatures because of very low lattice thermal conductivities, attributed to the liquid-like mobility of copper ions in the superionic phase. In this work, we present the potential of copper selenide to achieve a high figure of merit at room temperature, if the intrinsically high hole carrier concentration can be reduced. Using bromine as a dopant, we show that reducing the charge carrier concentration in Cu_(2−δ)Se is in fact possible. Furthermore, we provide profound insight into the complex defect chemistry of bromine doped Cu_(2−δ)Se via various analytical methods and investigate the conseque…
Thermoelectric properties of Zn-doped Ca_(3)AlSb_(3)
2012
Polycrystalline samples of Ca_(3)Al_(1)−_(x)Zn_(x)Sb_(3), with x = 0.00, 0.01, 0.02, and 0.05 were synthesized via a combined ball milling and hot pressing technique and the influence of zinc as a dopant on the thermoelectric properties was studied and compared to the previously reported transport properties of sodium-doped Ca_(3)AlSb_(3). Consistent with the transport in the sodium-doped material, substitution of aluminum with zinc leads to p-type carrier conduction that can be sufficiently explained with a single parabolic band model. It is found that, while exhibiting higher carrier mobilities, the doping effectiveness of zinc is lower than that of sodium and the optimum carrier concentr…
Design, assembly and characterization of silicide-based thermoelectric modules
2016
ID: 1143 In: Energy conversion and management, 13-21. Summary: Highlights•Novel silicide-based thermoelectric modules were experimentally investigated.•The modules produced high power of 1.04 W at 405 °C and 3.24 W at 735 °C.•An estimated module efficiency of 5.3% represent the highest reported for silicide systems.AbstractSilicides have attracted considerable attention for use in thermoelectric generators due mainly to low cost, low toxicity and light weight, in contrast to conventional materials such as bismuth and lead telluride. Most reported work has focused on optimizing the materials properties while little has been done on module testing. In this work we have designed and tested mod…
Design of a power conditioning unit for a Stirling generator in space applications
2012
The Free-Piston Stirling Generator (FPSG) is a thermal to electrical energy conversion system, based upon the thermal engine of the same name. Intensive research concerning the feasibility of the engine for its application in deep space and planetary missions has been conducted, primarily due to the potential increase in efficiency (−30%) over the currently used Radio-isotope Generators (RTGs). On the other hand, less attention has been paid to the power conditioning requirements and alternatives. The present work has investigated on the dynamics governing the FPSGs in order to assess the design requirements for the subsequent power-conditioning unit (PCU). Thereafter, two alternatives of A…
Optimization of a thermoelectric system for power generation realized by ‘‘hidden’’ components
2014
Abstract Today the utilization of renewable energy sources is very important to support the traditional ones, and also in order to reach the objectives fixed by the Kyoto Protocol. In this context, also well-known technologies related to the electric energy production, formerly not suitable – due to the poor technological level of the components or due to the high costs linked to the system efficiency – may now find a suitable collocation. Among these technologies, the thermoelectric effect may be very advantageous in some particular applications of small power. A power generation system utilizing this technology has been studied by the authors. This system utilizes the thermal difference b…
Concepts for medium-high to high temperature thermoelectric heat-to-electricity conversion: a review of selected materials and basic considerations o…
2015
Within the last decade, novel materials concepts and nanotechnology have resulted in a great increase of the conversion efficiency of thermoelectric materials. Despite this, a mass market for thermoelectric heat-to-electricity conversion is yet to be opened up. One reason for this is that the transfer of the lab records into fabrication techniques which enable thermoelectric generator modules is very challenging. By closing the gap between record lab values and modules, broad industrial applications may become feasible. In this review, we compare three classes of materials, all designed for medium-high to high temperature applications in the field of waste heat recovery: skutterudites, half…