The Superconducting and Normal Heat Capacities of Niobium

Data on the heat capacity of niobium in the normal and superconducting phases are presented in the temperature interval 2.5^∘{}K to 11^∘{}K. The normal heat capacity cₙ was found to be given by the usual relation: cₙ=γT+464T³Θ³, where γ=20.4×10^-4 cal/M deg² and Θ=252^∘K. The zero-field transition temperature T₀ was found to be 8.70^∘{}K±{}0.10^∘{}, and the heat capacity discontinuity Δc at this temperature to be 0.0368 cal/M deg. The heat capacity in the superconducting phase was found to depart from a T³ dependence below 5^∘{}K. The entire curve could not be represented by either the Koppe relation or the α model. The HT vs T curve deduced from the heat capacity data was found to be very nearly parabolic, with the value of H₀=2000 gauss and dHTdT at the zero-field transition temperature equal to 453 gauss/deg.