Standard Gibbs energy of formation of MgLa determined by solution calorimetry and heat capacity measurement from near absolute zero kelvin

Abstract The standard Gibbs energy of formation, Δ f G T ° , of MgLa in the temperature range from near absolute 0 to 525 K were determined by calorimetry. The heat capacities, C p , from 2 K to 525 K were measured by the relaxation method and DSC. Also, a thermal anomaly at 5.9 K, which appeared to be a superconductive phase transition, was found in the obtained C p values. The Δ f G T ° ( MgLa ) values were determined by combining the C p data with the standard enthalpy of formation at 298 K which was measured by the Calvet-type calorimeter using hydrochloric acid solution. From 2 to 300 K, the Δ f G T ° increases gradually, and it can be evaluated as a linear function of temperature above 300 K as follows: Δ f G T ° ( MgLa ) ( kJ mo l − 1 ) = − 39.236 − 6.9832 × 10 − 3 T + 2.1016 × 10 − 3 T log T + 1.9114 × 10 − 5 T 2 − 0.81004 T − 1 ± 7.40 ( 2 − 300 K ) , Δ f G T ° ( MgLa ) ( kJ mo l − 1 ) = − 41.100 + 9.9974 × 10 − 3 T ± 7.40 ( 300 − 525 K ) . This result is expected to be useful as basic thermodynamic data of Mg-based alloys.