Concentration-dependent oxygen diffusivity in YBa 2Cu 3O 6+x: I. Argon annealing studies

Abstract

Electrical resistance measurements were used to follow the isothermal in-diffusion characteristics in YBa 2Cu 3O 6+ x (YBCO) as a function of the initial oxygen content, x, at temperatures ranging from 650–708°C. Prior to the determination of oxygen in-diffusion rates, the initial oxygen contents in both polycrystalline and single crystal specimens were controlled by out-gassing in argon for different periods of time. An increasing dependence of the chemical diffusivity with decreasing initial oxygen content was observed which was typical of a vacancy diffusion mechanism. However, the magnitude of the dependence (and comparison with tracer diffusion studies) suggested that other factors (e.g., correlation effects or the thermodynamic factor) were responsible for the concentration dependence. The results are important for the development of atomic diffusion models for the oxygen mobility in YBCO.