Determination of valence of Cu in superconductingLa2−x(Sr,Ba)

Abstract

The measurement of Cu K-edge x-ray absorption near-edge structure of monovalent, divalent, and trivalent copper oxides has been used to identify the presence of different valence of copper in the La2 -"(Sr,Ba) Cu04 (x 0.0-0.3) system. The results indicate the coexistence of Curt and CuIII states in these compounds. Theoretical calculations based on a cluster of Cu040qLagLaSr predict the presence of nearly degenerate electronic ground states representing nominally CuII and Cu III configurations.The observation of high superconducting transition temperatures in doped La2Cu04 (Refs. 1-5) has created new interest in the long disputed valency of Cu in these compounds. ' The compound La2Cu04 has an orthorhombic structure and exhibits semiconducting behavior at low temperatures.

X-ray absorption spectroscopy and high-energy XRD study of the local environment of copper in antibacterial copper-releasing degradable phosphate glasses

“…A clear peak can be observed on the absorption edge of the Cu I reference compounds at 8981 eV. This peak is assigned to a 1s-4p transition [22,23]. A shoulder in the same position can be seen in the spectrum from the Ca 30 Na 15 P 45 Cu(I) 10 glass and also 10 -…”

“…Evidence for this comes from the weak shoulder at 8981 eV that corresponds to the 1s-4p transition in the Cu I reference materials [22,23]. However, the position of the main absorption edge for the glasses prepared using Cu 2 O is at an energy not significantly shifted from that of the Cu II reference materials, indicating the most of the copper is present in the higher oxidation state.…”

Structural and electrical changes in NdSrNiO4−δ by substitute nickel with copper

“…New interest in compounds of the formula Ln 2 CuO 4 (Ln=lanthanide) has been generated by the discovery of high-temperature superconductivity in doped La 2 CuO 4 [8]. The superconducting properties of this compounds generally have been considered to be dependent on the oxygen stoichiometry of the material and/or a variability of valencies of the Cu atoms [9].…”

Investigating Li2NiO2–Li2CuO2 Solid Solutions as High-Capacity Cathode Materials for Li-Ion Batteries

“…As shown in Figure 5b, the K-edge XANES of Cu in the pristine Li 2 Ni 0.8 Cu 0.2 O 2 exhibited two rising-edge transitions centered around 8984 and 8990 eV, which was in agreement with those of previous reported spectra, 21 corresponding to the electric dipole transitions from the 1s state to various np final states. 40 When charged to 3.8 V, the two rising edges around 8984, and 8990 eV almost vanished and ended at a more smooth main edge. Such dramatic change in the Cu K-edge XANES, after charging Li 2 Ni 0.8 Cu 0.2 O 2 to 3.8 V, was in agreement with those previously reported by Ruther et al and could be ascribed to the retained Cu 2+ .…”