Leonidov Ilia A, Markov Alexey A, Zavyalov Mikhail A, Merkulov Oleg V, Shalaeva Elisaveta V, Nikitin Sergey S, Tsipis Ekaterina V, Patrakeev Mikhail V
Institute of Solid State Chemistry, UB RAS, 620990 Ekaterinburg, Russia.
Osipyan Institute of Solid State Physics RAS, Moscow District, 142432 Chernogolovka, Russia.
Materials (Basel). 2022 Jun 21;15(13):4390. doi: 10.3390/ma15134390.
The structure, oxygen non-stoichiometry, and defect equilibrium in perovskite-type PrBaSrFeO ( = 0, 0.25, 0.50) synthesized at 1350 °C were studied. For all compositions, X-ray diffraction testifies to the formation of a cubic structure (S.G. Pm3¯m), but an electron diffraction study reveals additional diffuse satellites around each Bragg spot, indicating the primary incommensurate modulation with wave vectors about ±0.43a*. The results were interpreted as a sign of the short-order in both A-cation and anion sublattices in the areas of a few nanometers in size, and of an intermediate state before the formation of an ordered superstructure. An increase in oxygen deficiency was found to promote the ordering, whereas partial substitution of barium by strontium caused the opposite effect. The oxygen content in oxides as a function of oxygen partial pressure and temperature was measured by coulometric titration, and the data were used for the modeling of defect equilibrium in oxides. The simulation results implied oxygen vacancy ordering in PrBaSrFeO that is in agreement with the electron diffraction study. Besides oxidation and charge disproportionation reactions, the reactions of oxygen vacancy distribution between non-equivalent anion positions, and their trapping in clusters with Pr ions were taken into account by the model. It was demonstrated that an increase in the strontium content in PrBaSrFeO suppressed ordering of oxygen vacancies, increased the binding energy of oxygen ions in the oxides, and resulted in an increase in the concentration of p-type carriers.
研究了在1350℃合成的钙钛矿型PrBaSrFeO（ = 0、0.25、0.50）的结构、氧非化学计量比和缺陷平衡。对于所有组成，X射线衍射证明形成了立方结构（空间群Pm3¯m），但电子衍射研究揭示了每个布拉格斑点周围额外的漫散射卫星，表明存在波矢约为±0.43a*的初级非相称调制。这些结果被解释为在几纳米大小的区域中A阳离子和阴离子亚晶格中短程有序的迹象，以及有序超结构形成之前的中间状态。发现氧缺陷的增加促进了有序化，而用锶部分取代钡则产生相反的效果。通过库仑滴定法测量了氧化物中的氧含量作为氧分压和温度的函数，并将数据用于氧化物中缺陷平衡的建模。模拟结果表明PrBaSrFeO中存在氧空位有序化，这与电子衍射研究一致。该模型除了考虑氧化和电荷歧化反应外，还考虑了氧空位在非等效阴离子位置之间的分布反应以及它们在与Pr离子形成的簇中的俘获。结果表明，PrBaSrFeO中锶含量的增加抑制了氧空位的有序化，增加了氧化物中氧离子的结合能，并导致p型载流子浓度的增加。
