Heat capacity, entropy, formation energy and spin-fluctuation behavior of U3Si5 from 2.4 to 397.4 K

[摘要] U-Si intermetallic compounds are of considerable interest for their applications as accident-tolerant nuclear fuels. Here we present low-temperature heat capacity (LTHC) measurements of one of the U-Si phases, U3Si5, using a Quantum Design Physical Properties Measurement System (PPMS) from 2.4 to 397.4 K. We observed an upturn in C-p/T (T) below 10 K and have attributed this behavior to potential spin-fluctuations (SF) with an SF temperature (T-sf) of 27 K. An enhancement of LTHC was also observed, as manifested by a large electronic heat capacity coefficient (gamma(el)) of 342.9 mJ/mol.K-2. From the heat capacity data, the following thermodynamic parameters were determined: the characteristic Debye temperature (theta(D)) over the temperature range 30 - 397 K is 177 +/- 2 K, and the standard entropy (Delta S-298.15(0)degrees) is 283.3 +/- 5.7 J.mol(-1).K-1 (equivalent to 35.4 +/- 0.7 J.mol(-1).atom(-1).K-1). Combined with our previously measured formation enthalpy (Delta H-f(el)degrees) of U3Si5, the Gibbs free energy of formation of U3Si5 from the elements (Delta(f)G(el)degrees) was determined to be -45.2 +/- 9.0 kJ.mol(-1).atom(-1). (C) 2021 Elsevier B.V. All rights reserved.

[发布日期] 2021-12-15

[关键词] Uranium silicide;U3Si5;Thermodynamic properties;Heat capacity;Entropy;Enthalpy;Gibbs energy;Spin fluctuation;PPMS