OXYGEN DIFFUSION IN Y1-XPRXBA2CU3O7-DELTA OBSERVED BY RESISTIVITY MEASUREMENTS

In situ resistivity measurements have been used to monitor the oxygen uptake and removal for the ceramic system Y1-xPrxBa2Cu3O7-delta (YPBCO ) in the temperature range 300-1000 K. The study of the out-diffusion of oxygen was performed by annealing the oxygenated samples in ambient air at constant heating rates. We found that, independently of x, the oxygen concentration O7-delta is preserved up to 600 K, and that oxyg en diffuses out of the oxides at temperatures higher than 600 K. Howev er, the rate of oxygen removal from PrBa2Cu3O7-delta (PBCO) is greatly reduced as compared to the rate for pure YBa2Cu3O7-delta (YBCO), and decreases with increasing x in YPBCO. The study of the in-diffusion of oxygen was performed by annealing the deoxygenated samples in ambient air at constant heating rates. We found that, independently of x, the oxygen uptake takes place in the temperature range 550-750 K, where t he in-diffusion rate depends slightly on the Pr concentration. The obs erved resistivity change Delta rho(delta) for all of the YPBCO samples as they interchange oxygen with the gas phase indicates that the numb er of majority carriers in the oxides is mainly controlled by the oxyg en content delta and seems to be independent of the Pr concentration, at least for x less than or equal to 0.5.