Concentration-dependent oxygen diffusivity in YBa 2Cu 3O 6+x: II. Oxygen partial pressure studies

Abstract

Electrical resistance measurements were used to determine the equilibrium resistivity characteristics and the oxygen diffusion behavior in YBa 2Cu 3O 6+ x (YBCO) as a function of oxygen partial pressure at temperatures ranging from 450–850°C. The equilibrium resistivity values depended on the oxygen partial pressures as n = ϑLog ϱ/ ϑLog[ P(O 2)], where n ranged from approximately − 1 6 up to − 1 2 from low to high temperatures. A clear p-type to n-type transition was observed near 750°C for an oxygen content of 6.1 ( x = 0.1). Values of the oxygen exponent, n, for single crystal YBCO at 650°C and 708°C were similar to those for polycrystalline specimens. Measurements of the time-dependent resistivity behavior between different oxygen partial pressures yielded diffusion kinetics between well-established boundary values of the oxygen content, x. In single crystal specimens, the chemical diffusivity for oxygen in-diffusion was observed to increase with decreasing oxygen content. The kinetic data for the polycrystalline specimens between 450–850°C also depended on the oxygen concentration; however, the temperature dependence was non-Arrhenius.