Abstract
In this work, we studied the structural features of La1.9Ca0.1NiO4.11, which is considered a promising cathode material for intermediate temperature solid-oxide fuel cells (IT-SOFC). The effect of different pretreatments on the structural characteristics of the sample was studied using X-ray diffraction (XRD) and high-resolution transmission electron microscopy (HRTEM) in order to elucidate the origin of a peculiar change of lattice parameters observed earlier during in situ XRD studies. The XRD studies have shown that anisotropic broadening for reflections with a high Miller index l appears after tempering of a quenched (from 1100 °C) sample at 250 °C. This temperature is too low for the release/incorporation of oxygen into the structure but is sufficient for oxygen migration inside the structure. The HRTEM assisted us in revealing differences in the defect structure after different pretreatments. Based on obtained results, the following possible explanation was proposed. Observed additional microstrains and non-oriented planar defects as well as a decrease in the coherent scattering region size in the [00l] direction are caused by the non-homogeneous redistribution of interstitial oxygen in the structure during tempering.
Highlights
Researchers have paid close attention to the classes of complex, layered perovskite-like oxides structurally related to the Ruddlesden-Popper (R-P) [1–3]
The widespread electrochemical applications of Ln2NiO4+δ phases are characterised by a number of distinctive features: enhanced mixed ionic-electronic conductivity (MIEC), boosted chemical/thermal stability and mechano-thermal compatibility with electrolyte materials
The uniqueness of the above-mentioned combination of functional properties of Ln2NiO4+δ is attributed to the presence of highly mobile over-stoichiometric oxygen in the form of interstitial oxygen ions
Summary
Researchers have paid close attention to the classes of complex, layered perovskite-like oxides structurally related to the Ruddlesden-Popper (R-P) [1–3]. A strong antibate change of a and c lattice parameters in a temperature range from approximately 200 ◦C to 450 ◦C was observed during heating of the as-prepared sample in He flow.
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