Determination of the Oxygen Chain Ordering in REBa₂Cu₃O_7–δ by Electrical Conductivity Relaxation Measurements

Electrical conductivity relaxation was measured to investigate the kinetics of oxygen incorporation (in-diffusion process) and excorporation (out-diffusion process) in different epitaxial REBa2Cu3O7−δ thin films prepared by chemical solution deposition. The oxygen diffusion in these compounds happens in two distinct regimes with different activation energies, which depend on the compound. As the detailed X-ray analysis of similarly processed REBa2Cu3O7−δ films revealed, the transition temperature between these two regimes is compatible with a transition in the oxygen ordering in the Cu–O chains from the Ortho-II phase to the Ortho-I phase. These transitions may be of great importance for further optimization of the oxygenation process during the synthesis of these compounds but may depend not only on the rare-earth (RE) element but also on further factors such as variations of stoichiometry. The presented electrical conductivity measurements provide easy access to the determination of these transition temperatures.