Electrochemical intercalation of oxygen in lanthanum copper oxide at ambient temperature

Intrinsic tendency of electronic phase separation into two superconducting states inLa2−xSrxLorenz1, Li2, Honma3 et al. 2002Phys. Rev. B336290View full textAdd to dashboardCite

“…Originally high-pressure oxygen annealing was used to increase the O-content up to δ = 0.03 in La 2 CuO 4+δ . 5,7 However, electrochemical intercalation of oxygen has been proven to be superior to all other methods of oxidization 10,13,14 because of the low reaction temperature (close to room temperature), the higher oxygenation level (δ) that can be achieved, and the precise measurement and control of the doping level. We have carefully studied various electrochemical techniques and shown that samples so prepared are close to thermodynamic equilibrium for 0 < δ < 0.05 with a superconducting transition at T c ≈ 30 K as long as the intercalation rate was low.…”

“…We have carefully studied various electrochemical techniques and shown that samples so prepared are close to thermodynamic equilibrium for 0 < δ < 0.05 with a superconducting transition at T c ≈ 30 K as long as the intercalation rate was low. High intercalation rates, in particular for δ > 0.05, resulted in nonequilibrium samples with T c up to 45 K. 13,14 However, slow electrochemical oxidation followed by thermal annealing at 110 • C allows the samples to relax close to equilibrium and T c decreases to about 30 K. Outside the miscibility gap for δ > 0.05 a second superconducting transition with T c ≈ 15 K develops with annealing resulting in the two-step transition as described in the previous paragraph. 2,14 The appearance of different phases with increasing oxygen content is obviously related to the interstitial mobile oxygen ions and cannot be observed in the cation-doped La 2−x Sr x CuO 4 .…”

Evidence of Oxygen Intercalation and Mobility at Room Temperature in Oxides: An Electrochemical Quartz Microbalance Study of Intercalation in La2CuO4

“…These results agree with previously reported data on La 2 CuO 4 oxidation. [4][5][6][7][8] Figures 2a-5a show the cyclic voltammagrams (CVs) obtained on the 7-mm pellets attached to the quartz resonator, and the corresponding mass changes observed simultaneously (calculated from frequency changes using the BET area). The ratio of charge to mass calculated from both signals are shown in Figures 2c-5c for each solvent (water, methanol and propylene carbonate) and anion (oxygen and fluorine).…”

Lattice Dynamics Modified by Excess Oxygen in Nd2NiO4+δ: Triggering Low-Temperature Oxygen Diffusion

“…More intriguing is the fact that Nd 2 NiO 4+δ , like a few other nonstoichiometric oxides derived from the perovskite framework like the Brownmillerite-type Sr­(Fe,Co)­O 2.5 and K 2 NiF 4 -type Re 2 MO 4+δ (Re = La, Pr and M = Ni, Cu, Co), shows oxygen ionic mobility in an electrochemical reaction at room temperature. − This surprising behavior raises questions about the real microscopic transport mechanisms in these classes of materials when the temperature is as low as 300 K. Indeed oxygen ions are double negative charged and have large van der Waals radii so that elevated potential barriers normally hinder the hopping processes between interatomic sites at ambient temperature. A microscopic diffusion mechanism, based on the presence of a low-lying phonon mode, has been developed comparing inelastic neutron scattering data and DFT lattice dynamics calculations for the oxygen conductor SrFeO 2.5 and the nonconducting CaFeO 2.5 isostructural Brownmillerites .…”