Van der Pauw resistivity measurement and thermoelectric properties of Ba(8)Zn(x)Ni(y)Ge(46-x-y)

Abstract

In the present diploma thesis thermoelectric properties of type I clathrates Ba(8)Zn(x)Ni(y)Ge46-x-y are investigated. In addition a van der Pauw resistivity measurement system is designed, constructed and calibrated.Transport properties such as electrical resistivity, thermal conductivity and Seebeck coefficient were measured from 4 K to 600 K to assess the material's thermoelectric performance. This performance is scaled using the figure of merit ZT, which reaches 0.75 at 900 K for some samples.To measure resistivity of thin samples van der Pauw invented a new method. A sample holder was designed and constructed. Based on the graphical programming language LabView an automated measurement program was developed. Using the standard resistivity measurement system employed at the TU Wien, samples were gauged and used to asses the accuracy of the van der Pauw system.8