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Role of iron addition on grain boundary conductivity of pure and samarium doped cerium oxide

机译：铁的添加对纯and掺杂二氧化铈晶界电导的作用

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The present paper reports the effect of iron doping (0.5, 1.5 mol%) on the densification and electrical properties of cerium oxide (CeO2) and 20 mol% samarium-doped cerium oxide (SDC) electrolytes for intermediate temperature solid oxide fuel cell (ITSOFC) applications. A single-step solution combustion method was used for doping and the resultant powder was compacted into green pellets and subsequently sintered at 1200 degrees C. X-ray diffraction (XRD) studies indicated the presence of a cubic fluorite CeO2 structure without the formation of a secondary phase and the stoichiometry was confirmed by X-ray fluorescence spectroscopy. In the as-compacted green pellets, the XRD peak position shifted to lower or higher angles depending on the ionic radii of the dopants due to lattice level mixing. Addition of iron resulted in smaller crystallite sizes (< 11 nm) in the case of the green pellet, while an opposite trend was observed (> 40 nm) after sintering. Densification was found to be higher (95%) in iron-doped samples than in bare samples (< 90%) due to viscous flow sintering. Upon sintering the calculated strain value showed a lower value due to the segregation of iron from the lattice. Raman spectroscopic studies indicate that sintering marginally modifies the oxygen vacancy concentration in the SDC system, and found it to be higher than in CeO2. Addition of iron into the SDC improved the grain boundary conductivity 1.8 fold, but only a minor change was noticed for CeO2. The activation energy for the grain boundary conductivity was found to be lower for 1.5 mol% (1.06 eV) iron-doped SDC than for pure SDC (1.24 eV). Our results indicate that lattice level mixing of iron in SDC improves the density at relatively lower sintering temperatures and scavenges the grain boundary impurities, thereby increasing the grain boundary conductivity.
机译：本文报道了铁掺杂（0.5，1.5 mol％）对用于中温固体氧化物燃料电池（ITSOFC）的氧化铈（CeO2）和20 mol％掺mar氧化铈（SDC）电解质的致密化和电性能的影响）应用程序。使用单步溶液燃烧法进行掺杂，将所得粉末压制成生丸，随后在1200℃下烧结。X射线衍射（XRD）研究表明存在立方萤石CeO2结构，而未形成二氧化萤石。通过X射线荧光光谱法确认了第二相和化学计量。在压实的生坯中，由于晶格能级混合，取决于掺杂剂的离子半径，XRD峰位置移至较低或较高的角度。在生丸的情况下，铁的加入导致较小的微晶尺寸（＜11nm），而在烧结后观察到相反的趋势（＞ 40nm）。由于粘性流烧结，发现铁掺杂样品中的致密化程度高于裸露样品中的致密化程度（<90％）（<90％）。烧结后，由于铁从晶格中偏析，计算出的应变值显示出较低的值。拉曼光谱研究表明，烧结会稍微改变SDC系统中的氧空位浓度，并发现其高于CeO2中的空位浓度。在SDC中添加铁可将晶界电导率提高1.8倍，但CeO2的变化很小。发现1.5摩尔％（1.06eV）的铁掺杂的SDC的晶界电导率的活化能低于纯SDC的活化能（1.24eV）。我们的结果表明，在较低的烧结温度下，SDC中铁的晶格能级混合可提高密度，并清除晶界杂质，从而提高晶界电导率。

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