ChemInform Abstract: Observation of Superstructures in La2CuO4.09.

Abstract

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Electrochemically Induced Phase Changes in La2CuO4 During Cathodic Electrocatalysis

“…The as‐prepared material exists in an orthorhombic layered perovskite structure (space group Cmce, ICSD#56528) for which Rietveld refinement indicates unit cell dimensions of 5.3818, 5.4285 and 13.2095 Å (Figure A). LCO accommodates both interstitial oxygen and oxygen vacancies and is often presented as La 2 CuO 4+δ , with wide range of positive and negative δ values reported (Table S1) . The low relative molecular weight of oxygen makes it difficult to directly quantify δ in materials such as La 2 CuO 4 using laboratory powder X‐ray diffraction experiments.…”

“…The expansion of unit cell volume following anodization of LCO and the loss of Cu II observed by XPS confirm that this copper‐based redox process is associated with the insertion of interstitial oxygen ions . Comparison of the unit cell dimensions with previously reported structures for LCO suggests that anodization of the pristine La 2 CuO 4+0.12 yields a comparable La 2 CuO 4+0.11 at 1.3 V and an expanded La 2 CuO 4+0.15 at 1.9 V . The voltammetric characterization below this region is not well documented; we find LCO to be functionally stable when limited to voltages between −0.4 and 1.1 V vs. RHE.…”

Superconducting phases, charge ordering and possible correlation between them in La2CuO4.12

“…Fourth, no ab-plane charge ordering was observed in the samples with undepressed superconductivity in previous publications, in which similar bc-plane modulation patterns appear without considering the specific values of modulation vectors. For example, in the two superconducting La 2 CuO 4+δ samples, reported by Lagueyte et al (T c = 44 K and 32 K) [31] and Adachi et al (T c = 42 K) [49], the authors observed quite similar bc-plane TEM superstructure patterns as in this report. However, no clear trace of the present ab-plane modulation may be identified in their samples.…”

“…This indicates that two adjacent modulation layers become closer. In [31], Lagueyte et al observed a similar modulation structure in La 2 CuO 4.09 also at 100 K with a modulation vector of 0.22b * + 0.32c * . The modulation period derived from the vector is shorter than 25.5 in our La 2 CuO 4.12 .…”

“…This is actually a hint that some types of ordering and inhomogeneity exist in the superconducting phases. In fact, in La 2 CuO 4+δ , some superstructure reflections, charge ordering and Cu-O bond modulation have been detected by different methods [1,27,[31][32][33][34]. However, no detailed studies for mesoscopic structures (especially charge ordering) and their correlation to superconductivity has been done yet in relation to these interesting superconducting phases.…”