|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.
|Library ID:||AC14504076||Organisation:||E138 - Institut für Festkörperphysik||Publication Type:||Thesis
|Appears in Collections:||Thesis|
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checked on Apr 28, 2021
checked on Apr 28, 2021
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