The specific heat of sodium from 20 to 300 °K: the martensitic transformation

Abstract

Measurements on a cast sample and an extruded sample are reported. There is no significant difference in behaviour. No anomaly of the type reported by Dauphinee et al. (1954) was found. A thermal study of the martensitic transformation showed a large specific-heat anomaly in the reversion region and a specific heat dependent on thermal history in the two-phase region. The heat of transformation from hexagonal close-packed to body-centred cubic sodium is deduced to be about 10 cal/g atom and the Debye temperatures of the two phases at 20 °K to be 160 and 153 °K respectively. The entropy at 298.15 °K is 12.24 ± 0.12 cal/°K g atom.