A THEORETICAL-ANALYSIS OF THE RESISTANCE CHANGES ACCOMPANYING OXYGEN DIFFUSION IN YBA2CU3OX

A theoretical analysis of resistance changes accompanying oxygen diffu sion in YBa2Cu3Ox single crystals as a function of time has been carri ed out. Normalized resistance vs. time plots for different starting ox ygen concentrations have been calculated for both in- and out-diffusio n of oxygen. Shape of theoretical plots :is seen to depend on starting oxygen concentration, showing that simple exponential time dependence of resistance, generally used to calculate diffusion coefficients, is not valid. A re-analysis of resistance data measured at different oxy gen concentrations by LaGraff and Payne [J.R. LaGraff, D.A. Payne, Phy sica C 212 (1993) 470, 473.] shows that the diffusion coefficient is n early independent of concentration and is the same for both in- and ou t-diffusion. (C) 1998 Elsevier Science B.V. All rights reserved.