Abstract

The work is focused on the studying of structural peculiarities, electronic and ionic conductivity, and thermomechanical properties of perovskite-like compositions in Ba_{1 –x}Sr_xFe_{1 –y}Ti_yO_{3 – δ} and BaTi_0.5Fe_{0.5 –z}Ce_zO_{3 – δ} systems. The cubic structure was shown to be preserved on the substituting of up to 50% of barium cations for strontium in A-sublattice of (Ва,Sr)(Fe,Ti)O_{3 – δ}, while further doping leads to transition of the crystal lattice into its hexagonal modification. The introducing of Ce into the B-sublattice suppressed this transformation to some extent. Substitution of titanium or cerium for iron reduced both electronic and ionic conductivity, due to the lowering of concentration of the sites available for electron transfer in the B-sublattice, lower oxygen nonstoichiometry, and larger Ti–O and Ce–O bond energy, as compared to that for Fe–O. Generally, the stabilization of the cubic structure ensures larger mobility of electronic and especially ionic charge carriers. The increasing of Ba content in the (Ва,Sr)(Fe,Ti)O_{3 – δ} perovskite with cubic structure improved its ionic conductivity and resulted in an elongation of Fe–O bond and decreasing of the degree of overlapping between iron and oxygen atoms, which leads to lower electronic conductivity. The thermal expansion coefficients correlate with the ionic conductivity; the minimum expansibility was observed for the Ba-enriched compositions with hexagonal structure. It was demonstrated that the oxygen permeability of the (Ва,Sr)(Fe,Ti)O_{3 – δ} and Ва(Fe,Ti,Се)O_{3 – δ} dense membranes is limited by the oxygen diffusion in the membrane phase bulk and the oxygen surface-exchange kinetics.

中文翻译：

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钙钛矿型Ba 1 – x Sr x Fe 1 – y Ti y O 3 –δ和BaTi 0.5 Fe 0.5 – z Ce z O 3 –δ固溶体的混合电子和离子电导率

摘要

这项工作的重点是研究Ba _{1 – x} Sr _x Fe _{1 – y} Ti _y O _{3 –δ}和BaTi _0.5 Fe _{0.5 – z} Ce _z中钙钛矿状成分的结构特性，电子和离子导电性以及热机械性能。O _3-δ系统。结果表明，在（Ва，Sr）（Fe，Ti）O _3- δA-亚晶格中，锶的钡取代量高达50％时，立方结构得以保留。，而进一步掺杂导致晶格转变成其六边形修饰。将Ce引入B亚晶格在某种程度上抑制了这种转变。钛或铈代替铁会降低电子和离子传导率，这是因为降低了B亚晶格中可用于电子转移的位点的浓度，较低的氧非化学计量以及较大的Ti–O和Ce–O键能。与Fe-O相比。通常，立方结构的稳定性确保了电子，尤其是离子载流子的更大迁移率。（Ва，Sr）（Fe，Ti）O _3-δ中Ba含量的增加具有立方结构的钙钛矿提高了其离子电导率，并延长了Fe–O键的延伸，并降低了铁与氧原子之间的重叠程度，从而降低了电子电导率。热膨胀系数与离子电导率相关。对于具有六方结构的富含Ba的组合物，观察到最小的膨胀性。结果表明，（Ва，Sr）（Fe，Ti）O _3-δ和Ва（Fe，Ti，Се）O _3-δ致密膜的透氧性受到膜相体积和相中氧扩散的限制。氧表面交换动力学。