The low temperature heat capacities of Na4UO5 and Na4NpO5 have been measured
for the first time in the temperature range 1.9 to 292 K using a PPMS instrument (Physical Properties Measurement System, Quantum Design). The heat capacity and entropy values at 298.15 K have been derived at Cp (Na4UO5,cr, 298:15K) = (219.0±6.6) J.K-1.mol-1, S0(Na4UO5, cr,298:15K) = (247.4±7.4) J.K-1.mol-1, Cp(Na4NpO5,cr,298:15 K) = (220.8±6.6) J.K-1.mol-1, and S0(Na4NpO5,cr,298:15K) = (247.2±7:4) J.K-1.mol-1. When combined with the enthalpies of formations reported in the literature, these data yield standard entropies of formation at ΔS0f (Na4UO5,cr, 298:15K) = -(520.9±7.4) J.K-1.mol-1and ΔS0f (Na4NpO5,cr,298:15K) = -(521.3±7.4) J.K-1.mol-1, and standard Gibbs energies of formation at ΔG0f (Na4UO5, cr,298:15K) = -(2301.7±3.1) kJ.mol-1 and
ΔG0f (Na4NpO5,cr,298.15K) = -(2160.0±6:1) kJ.mol-1.
SMITH Anna;
GRIVEAU Jean-Christophe;
COLINEAU Eric;
RAISON Philippe;
WALLEZ G;
KONINGS Rudy;
2016-01-05
ACADEMIC PRESS LTD- ELSEVIER SCIENCE LTD
JRC95135
0021-9614,
https://publications.jrc.ec.europa.eu/repository/handle/JRC95135,
10.1016/j.jct.2015.08.003,
