Nikitin Sergey S, Markov Alexey A, Merkulov Oleg V, Chukin Andrey V, Patrakeev Mikhail V
Institute of Solid State Chemistry, UB RAS, 620990 Ekaterinburg, Russia.
Institute of Solid State Chemistry and Mechanochemistry, SB RAS, 630128 Novosibirsk, Russia.
Dalton Trans. 2021 Dec 14;50(48):17967-17980. doi: 10.1039/d1dt03628a.
The oxygen content in LaSrFeMnO, measured by coulometric titration in a wide range of oxygen partial pressure at various temperatures, was used for defect chemistry analysis. The obtained data were well approximated by a model assuming defect formation in LaSrFeMnO Fe and Mn oxidation reactions and charge disproportionation on Fe and Mn ions. The partial molar enthalpy and entropy of oxygen in LaSrFeMnO obtained by statistical thermodynamic calculations were found to be in satisfactory agreement with those obtained using the Gibbs-Helmholtz equations, thus further confirming the adequacy of the model. The impact of manganese substitution on defect equilibrium in LaSrFeMnO was shown to be attributed to a lower enthalpy of Mn oxidation reaction ( for the oxidation of Fe) and the charge disproportionation reaction on Mn ( for that on Fe). The former makes Mn ions more resistant to reduction than Fe. The latter favors the presence of Mn, Mn, and Mn ions in oxides in comparable concentrations. The distribution of charge carriers over iron and manganese ions was determined as a function of oxygen content in LaSrFeMnO.
通过在不同温度下的宽氧分压范围内进行库仑滴定法测量LaSrFeMnO中的氧含量，用于缺陷化学分析。所获得的数据通过一个模型得到了很好的近似，该模型假设在LaSrFeMnO的Fe和Mn氧化反应中形成缺陷以及Fe和Mn离子上的电荷歧化。通过统计热力学计算得到的LaSrFeMnO中氧的偏摩尔焓和熵与使用吉布斯 - 亥姆霍兹方程获得的结果吻合良好，从而进一步证实了该模型的适用性。结果表明，锰取代对LaSrFeMnO中缺陷平衡的影响归因于较低的Mn氧化反应焓（相对于Fe的氧化）以及Mn上的电荷歧化反应（相对于Fe上的）。前者使Mn离子比Fe更耐还原。后者有利于氧化物中Mn³⁺、Mn⁴⁺和Mn²⁺离子以相当的浓度存在。确定了LaSrFeMnO中电荷载流子在铁和锰离子上的分布作为氧含量的函数。
