Specific heat anomaly at the α-α′ phase transition in NbH 0.3

Abstract

Measurements of the specific heat at the α-α′ phase transition of hydrogen in niobium are reported. The specific heat displays an unexpected rounded peak, which is compared with predictions of the molecular field approximation and with the specific heat derived from the coexistence curve of the incoherent α-α′ phase transition. In the latter case there is satisfactory agreement. The shape of the coexistence curve and the specific heat anomaly are dominated by internal stress fields which are due to dislocations.