Ling Yihan, Wang Fang, Budiman Riyan Achmad, Nakamura Takashi, Amezawa Koji
Institute of Multidisciplinary Research for Advanced Materials, Tohoku University, 2-1-1 Katahira Aoba-ku, Sendai 980-8577, Japan.
Phys Chem Chem Phys. 2015 Mar 21;17(11):7489-97. doi: 10.1039/c4cp05719h.
Oxygen nonstoichiometry of the Ruddlesden-Popper oxide Sr3Fe2O7-δ was measured at intermediate temperatures (773-1073 K) by coulometric titration and high temperature gravimetry. The oxygen nonstoichiometric behavior was analyzed using the defect equilibrium model with localized electrons. From the defect chemical analysis, estimated oxygen vacancy concentration at the O3 sites increases and at the O1 sites decreases with the increasing temperature. This characteristic behavior is considered to be caused by the redistribution of oxygen and vacancies between the O1 and O3 sites. The obtained thermodynamic quantities of the partial molar enthalpy of oxygen, h(O) - h°(O), and the partial molar entropy of oxygen, s(O) - s°(O), calculated from the Gibbs-Helmholtz equation are in good agreement with those from the statistical thermodynamic calculation based on the defect equilibrium model, indicating that the proposed defect equilibrium model is reasonable.
通过库仑滴定法和高温重量法在中间温度（773 - 1073 K）下测量了Ruddlesden - Popper氧化物Sr3Fe2O7-δ的氧非化学计量比。使用具有局域电子的缺陷平衡模型分析了氧非化学计量行为。通过缺陷化学分析可知，随着温度升高，O3位点处估计的氧空位浓度增加，而O1位点处的氧空位浓度降低。这种特征行为被认为是由O1和O3位点之间氧和空位的重新分布引起的。根据吉布斯 - 亥姆霍兹方程计算得到的氧的偏摩尔焓h(O) - h°(O)和氧的偏摩尔熵s(O) - s°(O)的热力学量，与基于缺陷平衡模型的统计热力学计算结果吻合良好，表明所提出的缺陷平衡模型是合理的。
