Investigation of the superconducting transition point of niobium as reference temperature

The superconducting transition point of a high-purity niobium single crystal was investigated in regard to its applicability as reference temperature. The transition between the normal and the superconducting phase was pointed out with mutual inductors. The transition temperature was measured with germanium resistance thermometers. The thermal hysteresis curve showed the reproducibility of the transition temperature. The measured residual resistance ratios give information on the degree of crystal purity. All measurements led to the conclusion that the superconducting transition point of niobium could be used as reference temperature