Abstract
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 Cp/T (T) below 10 K and have attributed this behavior to potential spin-fluctuations (SF) with an SF temperature (Tsf) of 27 K. An enhancement of LTHC was also observed, as manifested by a large electronic heat capacity coefficient (γel) of 342.9 mJ/mol•K2. From the heat capacity data, the following thermodynamic parameters were determined: the characteristic Debye temperature (θD) over the temperature range 30 – 397 K is 177 ± 2 K, and the standard entropy (Δ0298.15S∘) 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 (ΔfHel∘) of U3Si5, the Gibbs free energy of formation of U3Si5 from the elements (ΔfGel∘) was determined to be –45.2 ± 9.0 kJ•mol−1•atom−1.
| Original language | English |
|---|---|
| Article number | 153282 |
| Journal | Journal of Nuclear Materials |
| Volume | 557 |
| DOIs | |
| State | Published - Dec 15 2021 |
| Externally published | Yes |
Funding
We are grateful to two anonymous reviewers for helpful comments. Research presented in this article was supported by the Laboratory Directed Research and Development (LDRD) program at Los Alamos National Laboratory (LANL) under project number 20180007. JLB acknowledges the support of the Seaborg Institute through a LANL Seaborg postdoctoral fellowship. PPMS experiments were performed at the Center for Integrated Nanotechnologies (CINT), an Office of Science User Facility operated for the U.S. Department of Energy Office of Science. LANL, an affirmative action/equal opportunity employer, is managed by Triad National Security Administration of the U.S. Department of Energy under contract number 89233218CNA000001. We are grateful to two anonymous reviewers for helpful comments. Research presented in this article was supported by the Laboratory Directed Research and Development (LDRD) program at Los Alamos National Laboratory (LANL) under project number 20180007. JLB acknowledges the support of the Seaborg Institute through a LANL Seaborg postdoctoral fellowship. PPMS experiments were performed at the Center for Integrated Nanotechnologies (CINT), an Office of Science User Facility operated for the U.S. Department of Energy Office of Science. LANL, an affirmative action/equal opportunity employer, is managed by Triad National Security Administration of the U.S. Department of Energy under contract number 89233218CNA000001. The raw/processed data required to reproduce these findings cannot be shared at this time due to technical or time limitations.
Keywords
- Enthalpy
- Entropy
- Gibbs energy
- Heat capacity
- PPMS
- Spin fluctuation
- Thermodynamic properties
- USi
- Uranium silicide