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INFLUENCE OF THE DIMENSIONS OF THE SAMPLE ON THE MEASUREMENTS OF HALL AND SEEBECK COEFFICIENT

Authors: Šraitrová Kateřina | Čermák Patrik | Kucek Vladimír | Drašar Čestmír

Year: 2017

Type of publication: ostatní - přednáška nebo poster

Page from-to: nestránkováno

Titles:

Language	Name	Abstract	Keywords
eng	INFLUENCE OF THE DIMENSIONS OF THE SAMPLE ON THE MEASUREMENTS OF HALL AND SEEBECK COEFFICIENT	Measurements of Hall and Seebeck coefficient are essential for research of thermoelectric materials. The aim of this work was to investigate the influence of the dimensions of the sample on the measurements of these two coefficients. Two single crystals of well-known thermoelectric material Bi2Se3 were prepared. Samples of desired dimensions for our measurements were prepared with use of the electro-erosive cutter. We studied the influence of dimensions (shorting of the samples) and the influence of the shape (oblique cut) of the sample on the measurements. The statistical deviation between our measurements is about 10% We obtained interesting results in measurements of Hall coefficient and electrical conductivity in case of shorting of the sample. According to the theory the measurement becomes inaccurate if the ratio between length and width of the sample is smaller than 2 [1, 2, 3]. This is in contradiction with our results. From our measurements it follows that all of the measured values lie in the 10% deviation even if the ratio between length and width of the sample is smaller than 2 (1.1). Greater deviation in the results was detected when the ratio was smaller than 1 (0.9). In this case the deviation of Hall constant was about 30% and of the electrical conductivity about 15%. In case of oblique cut of the sample our results changed dramatically (30% in Hall coefficient and 15% in electrical conductivity). The results of Seebeck coefficient showed no significant deviation in all types of measurements. We also studied the influence of the measuring equipment, the stability of the samples and the attachment of current-introducing contacts (AquaDAG, Ni-paste, Ag-paste). The way of the attachment of the current-introducing contacts has in our temperature range (from the temperature of liquid nitrogen to 200°C) and our experiment arrangement (alternating current) no influence on the measurement.	Hall coefficient, Seebeck coefficient, thermoelectric materials