High-Tcsuperconductors as passive thermo-elements

The figure of merit for energy conversion by a thermocouple involves a combination of the properties of the two branches. Although it often has a value that is close to the average of the branch figures of merit, this is not always the case. In particular, there is no positive thermo-electric material that matches the negative thermo-elements, made from bismuth-antimony, that are useful at low temperatures. It is shown that there is some merit in using a material with a very low Seebeck coefficient, but with a very high ratio of electrical conductivity to thermal conductivity as the positive branch. Consideration is given to the use of the new high-temperature superconductors for this purpose. Experiments on the latter in a magnetic field at liquid-nitrogen temperature are reported.