Title: Thermoelektrizität in off-stöichiometrischen Fe2 V1-x WxAl Heusler Systemen
Other Titles: Fe tief 2 V tief 1-x Wtief x
Language: Deutsch
Authors: Rehak, Johannes Wolfgang 
Qualification level: Diploma
Advisor: Bauer, Ernst 
Issue Date: 2017
Number of Pages: 73
Qualification level: Diploma
Abstract: 
Thermoelectric materials offer the possibility to convert heat that would be wasted into the environment and turn it into electric energy. Especially Heusler-alloys have recently attracted renewed interest for their application in thermoelectric devices. Based on measurements on tungsten doped Fe2VAl-alloys, two series consisting of four probes each, have been synthesized. Additionally, to the doping with tungsten the (Fe-W-V)/Al-ratio has been varied. Thus, the chemical formula was ((Fe2/3(WxV1x)1/3)yAl1y with x = Furthermore, a measurement setup was modified to measure the Hall effect by using the six-point-method (6P-method) instead of the already existing Van-der-Pauw-method. Additionally, the crystal structure was studied by using power diffraction. The analysis of the executed measurements resulted in a small decrease of the electrical resistivity compared to the non-offstochiometric probes, while there was no significant change in the Seebeck coefficient and the thermal conductivity. Thus, increasing the ZT-value with a highest of ZT = 0,23 at room temperature T = 300K, which was calculated for the second probe of the second series ((Fe2/3(W0,1V0,2)1/3)0,76Al0,24). Moreover, the result of the behaviour for the Seebeck coefficient as a function of the valence electron concentration (VEC) of Fe2VAl based alloys was confirmed with a small deviation. The Hall effect measurements affirmed the results concerning the dominating type of charge carriers in both series. Additionally, a rise in carrier charge density was noticed in the second series. By comparing the results of electrical resistivity measurements which were gained using the 6P-method and inside the cryogenic receptacles a systematic error concerning the Hall effect measurements setup was identified.
Keywords: Heusler System
Heusler systems
URI: https://resolver.obvsg.at/urn:nbn:at:at-ubtuw:1-134641
http://hdl.handle.net/20.500.12708/5700
Library ID: AC14504076
Organisation: E138 - Institut für Festkörperphysik 
Publication Type: Thesis
Hochschulschrift
Appears in Collections:Thesis

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