Heat capacities of lad x (2.5 ⩽ x ⩽ 3) from 1 to 300 K

Abstract

The heat capacities of LaD x (2.5 ⩽ x ⩽ 3) were measured in the temperature range from 1 to 300 K. Four sharp heat capacity peaks were found in LaD 3.0 at 211, 230.5, 233.5 and 274 K indicating the existence of five polymorphic forms. Only one sharp heat capacity peak was observed at 251 K for LaD 2.91 and LaD 2.76, while no peaks were observed in the heat capacity of LaD 2.53. The electronic specific heat constant γ was found to be zero for LaD x (2.76 ⩽ x ⩽ 3), indicating that at low temperatures these alloys are semiconductors or semimetals with a small number of conduction electrons. The non-zero γ value for LaD 2.53 indicates the existence of a few conduction electrons. The thermodynamic functions S 298.15 o and (H 298.15 o−H 0) o) T were determined.