The Effects of Gaseous Helium and Nitrogen on the Thermopower Measurements: A Note of Concern for the Discrepancy of the Results Observed in High Temperature Superconductors

We investigated the effects of gaseous helium and nitrogen on the thermopower measurements. It was observed that for a constant power supply to the heater, the temperature gradient ΔT established across the sample, lead (Pb) in our case, depended upon the thermal conductivity of the gas with which the sample vessel was filled. This affected the estimation of the thermopower S since the measured ΔT was probably a pseudo value due to the heat losses that occurred in the presence of a heat conducting gas. A qualitative model was introduced to account for the physical processes taking place during the thermopower measurements for vessels filled with heat conducting gases. The effects of gas adsorption and desorption to and from the sample respectively are also discussed.