High temperature setup for measurement of Hall coefficient and electrical conductivity of thermoelectric materials.

An experimental setup has been developed for the simultaneous measurement of the Hall coefficient (RH) and electrical conductivity (σ) of thermoelectric (TE) specimens in the temperature range of 300-700 K. The van der Pauw geometry is utilized for the RH and σ measurements. The sample holder geometry has been designed for diverse TE specimen dimensions and easy sample mounting. A special feature of the holder geometry is that the same sample can be used for other relevant thermoelectric measurements such as the Seebeck coefficient and thermal diffusivity. This minimizes measurement errors associated with compositional or doping inhomogeneities. In the absence of high temperature standard reference materials for Hall coefficient measurements, silicon samples with different doping concentrations have been used to verify the accuracy of the instrument. Additionally, the electrical conductivity data have been validated by measurements on the same samples in a calibrated setup. Repeat measurements indicate a maximum standard deviation of ±3% and ±0.5% for the RH and σ data in the studied temperature range. Furthermore, comparisons with the calibrated setup indicate deviations within ±3% for the σ data. The suitability of the measurement setup for TE specimens has been demonstrated using measurements on n-type (Mg2Sn) and p-type (Mg3Sb2) specimens with carrier concentrations in the range of 1019-1020 cm-3.