Oxygen nonstoichiometry and ionic transport in La<sub>2sub>Ni(Fe)O<sub>4 + δsub>

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• 作者：E.V. Tsipis ; E.N. Naumovich ; A.L. Shaula ; M.V. Patrakeev ; J.C. Waerenborgh ; V.V. Kharton
• 关键词：Lanthanum nickelate ; Oxygen permeability ; Ionic conductivity ; Surface exchange kinetics ; Oxygen hyperstoichiometry
• 刊名：Solid State Ionics
• 出版年：2008
• 出版时间：31 March 2008
• 年：2008
• 卷：179
• 期：1-6
• 页码：57-60
• 全文大小：497 K

文摘

The steady-state oxygen permeation fluxes through dense La<sub>2sub>NiO<sub>4 + δsub> and La<sub>2sub>Ni<sub>0.9sub>Fe<sub>0.1sub>O<sub>4 + δsub> ceramics, studied at 973–1223 K for membrane thickness range 0.6 to 2.0 mm, are limited by both bulk ambipolar conductivity and surface exchange kinetics. The permeability data, in combination with total conductivity and equilibrium p(O<sub>2sub>)–T–δ diagrams, were used in numerical regression analysis to extract the local chemical potential gradients, defect concentrations, partial conductivities and exchange rates. Doping with iron was found to increase oxygen-ion mobility in K<sub>2sub>NiF<sub>4sub>-type lanthanum nickelate at 1173–1223 K, whilst activation energies remain essentially similar, 69–80 kJ/mol. At lower temperatures, the surface kinetics and ionic transport in La<sub>2sub>Ni<sub>0.9sub>Fe<sub>0.1sub>O<sub>4 + δsub> become both slower than those in La<sub>2sub>NiO<sub>4 + δsub>. Possible defect-interaction and exchange mechanisms relevant to this behavior are briefly discussed.