Thermodynamic assessment of the NaH ↔ Na3AlH6 ↔ NaAlH4 hydride system

Thermodynamic properties of hydrides, NaH, Na3AlH6 and NaAlH4 which can be a promising candidate for a hydrogen storage material system, were critically assessed by analyzing available piecewise literature information on thermodynamic properties using the CALPHAD method. Through the assessment, a critical evaluation on the reliability of individual literature data on thermodynamic properties of the NaH–Na3AlH6–NaAlH4 hydride system could be made, and a self-consistent thermodynamic description could be obtained. The finally assessed thermodynamic description can reproduce various thermodynamic properties of individual hydrides and phase equilibria among hydrides in reasonable agreement with relevant experimental and high-level calculation data, and provide a reference data that can be used for comparison with high-level calculations and for further thermodynamic assessments of higher order systems.