Sample probe to measure resistivity and thermopower in the temperature range of 300–1000K

Abstract

We have fabricated and tested a sample probe that can measure resistivity (ρ) and thermopower (α) on either bar or rod shaped samples over a temperature span of 300–1000K. The design allows us to perform measurements both in vacuum as well as in inert atmosphere and hence suitable for any oxygen sensitive bulk samples. The main feature is the spring assisted pressure contacts between the sample and the two silver blocks, on which the electrical leads as well as thermocouples are mounted. This enables us to establish good thermal contacts over the entire temperature range of measurements between the sample and the thermocouples. To measure the thermopower, a slowly varying temperature difference (ΔT) is generated across the sample by using a small heater. The resulting slope of thermo-emf (ΔV) vs temperature difference (ΔT) plot is used to obtain the thermopower at any temperature. Resistivity is measured in sequence by a linear four-probe method at the same temperature. Hence in a single experiment, both resistivity and thermopower can be measured. Test measurements carried out on Ni and W standards yielded an accuracy of about few percent for both ρ and α.