CAUSES OF CHANGE IN THERMOELECTRIC CHARACTERISTICS OF TUNGSTEN-RHENIUM THERMOCOUPLES

A study has been made of the causes of thermal and emf variation under vacuum and in the most favorable media, viz. , hydrogen and oxygen. The main causes of instability are component diffusion along the wires, recrystallization and component redistribution in the temperature pattern, and the tendency for deposits of a second phase to form in VR-3-5 alloys, which is due to the anomalous electronic structure. The stability of such thermocouples is improved by using another material with a similar electronic structure.