Sereda Vladimir V, Malyshkin Dmitry A, Ivanov Ivan L, Tsvetkov Dmitry S, Zuev Andrey Yu, Maignan Antoine
Institute of Natural Sciences and Mathematics, Ural Federal University, 19 Mira Street, Yekaterinburg 620002, Russia.
Laboratoire CRISMAT, UMR 6508 Normandie Université, CNRS, ENSICAEN, UNICAEN, 6 bd du Maréchal Juin, 14050 Caen Cedex 4, France.
Inorg Chem. 2021 Dec 6;60(23):18141-18153. doi: 10.1021/acs.inorgchem.1c02746. Epub 2021 Nov 16.
The oxygen nonstoichiometry, δ, and oxidation enthalpy, Δ, of double perovskites RBaCoO (R = Sm or Eu) were simultaneously measured depending on the temperature and oxygen partial pressure, . Theoretical equations for Δ(, δ) and (, δ) were derived from the defect structure model based on the oxygen exchange and cobalt disproportionation reactions. These equations were fitted independently to each of the experimental Δ(, δ) and (, δ) data sets. The resulting enthalpies of defect reactions were found to be almost the same irrespective of the calculation method. In other words, the models, describing satisfactorily the data, can be used to calculate both compositional dependences and redox thermodynamics of RBaCoO (R = Sm or Eu). In addition, from the previously published data and the data presented here, trends were determined in the defect reaction thermodynamics of RBaCoO (R = La, Pr, Nd, Sm, Eu, Gd, or Y). Drop calorimetric measurements were performed in air to obtain enthalpy increments for RBaCoO (R = Sm or Eu) with variable oxygen content because the samples lost oxygen upon being heated in the calorimetric cell. As-obtained data were used to calculate the functional dependences of enthalpy increments of EuBaCoO and SmBaCoO with a constant oxygen content. In addition, as an example of practical application-oriented calculations for solar energy conversion and oxygen storage, the performances at equilibrium of RBaCoO (R = Pr, Sm, Eu, or Gd) were evaluated and compared to those of SrFeO as a reference material.
根据温度和氧分压，同时测量了双钙钛矿RBaCoO（R = Sm或Eu）的氧非化学计量比δ和氧化焓Δ。基于氧交换和钴歧化反应的缺陷结构模型推导出了Δ(, δ)和(, δ)的理论方程。这些方程分别独立拟合到每个实验Δ(, δ)和(, δ)数据集。结果发现，无论计算方法如何，缺陷反应的焓几乎相同。换句话说，能令人满意地描述数据的模型可用于计算RBaCoO（R = Sm或Eu）的成分依赖性和氧化还原热力学。此外，根据先前发表的数据和本文给出的数据，确定了RBaCoO（R = La、Pr、Nd、Sm、Eu、Gd或Y）缺陷反应热力学的趋势。在空气中进行滴定量热测量，以获得氧含量可变的RBaCoO（R = Sm或Eu）的焓增量，因为样品在量热池中加热时会失去氧。所得数据用于计算氧含量恒定的EuBaCoO和SmBaCoO焓增量的函数依赖性。此外，作为面向太阳能转换和氧存储的实际应用计算的一个例子，评估了RBaCoO（R = Pr、Sm、Eu或Gd）在平衡时的性能，并与作为参考材料的SrFeO的性能进行了比较。
