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Heat capacity, entropy, formation energy and spin-fluctuation behavior of U3Si5 from 2.4 to 397.4 K
Journal of Nuclear Materials ( IF 3.1 ) Pub Date : 2021-09-04 , DOI: 10.1016/j.jnucmat.2021.153282
Jason L. Baker 1 , Josh T. White 2 , Aiping Chen 3 , Tasheima Ulrich 2 , Robert R. Roback 1 , Hongwu Xu 1
Affiliation  

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.



中文翻译:

U3Si5 从 2.4 到 397.4 K 的热容量、熵、形成能和自旋波动行为

U-Si 金属间化合物因其作为容灾核燃料的应用而备受关注。在这里,我们使用量子设计物理特性测量系统 (PPMS) 从 2.4 到 397.4 K 展示了 U-Si 相之一 U 3 Si 5的低温热容 (LTHC) 测量值。我们观察到 C p的上升/T (T) 低于 10 K 并将这种行为归因于潜在的自旋波动 (SF),SF 温度 (T sf ) 为 27 K。还观察到 LTHC 的增强,表现为大的电子热容系数(γ el ) 为 342.9 mJ/mol•K 2. 根据热容量数据,确定了以下热力学参数: 特征德拜温度 (θD) 在 30 – 397 K 的温度范围内为 177 ± 2 K,标准熵 (Δ0298.15) 是 283.3 ± 5.7 J•mol -1 •K -1(相当于 35.4 ± 0.7 J•mol -1 •atom -1 •K -1)。结合我们之前测量的形成焓(ΔFH电子)U的3的Si 5,形成U形的吉布斯自由能3的Si 5从元件(ΔFG电子) 被确定为 –45.2 ± 9.0 kJ•mol -1 •atom -1

更新日期:2021-09-16
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