Hydrogen absorption–desorption characteristics of the LaNi 5Sn intermetallic compound

Abstract

The pressure–composition–temperature (P–C–T) relations in the LaNi 5Sn–H system were measured volumetrically at temperatures between 258 and 423 K. Two hydride phases, β-LaNi 5SnH 2 and γ-LaNi 5SnH 3 are formed in this system in addition to the α-solid solution with a limiting H content of 0.3 H atoms per formula unit. The calculated work loss due to hysteresis is rather small, 112 J (mol H) −1 at 298 K. The partial molar enthalpy and entropy calculated for the formation of the β-LaNi 5SnH 2 are −18.5±0.8 kJ (mol H) −1 and −53.7±2.3 J (K mol H) −1, respectively. An advanced van der Waals lattice gas model was applied to fit the isotherms. The critical temperature of the LaNi 5SnH 2 equals T C=421±17 K.