CO-2 DECOMPOSITION KINETICS OF YBA2CU3O7-X VIA INSITU ELECTRICAL-CONDUCTIVITY MEASUREMENTS

In situ electrical conductivity measurements were employed to study the kinetics of decomposition of YBa2Cu3O7-x in flowing 5% CO2/95% O2 atmosphere at 815-degrees-C. Three regimes could be observed in the decay of the conductivity with time, interpreted as corresponding to nucleation over the initial 5 - 10 min, rapid formation of Y2Cu2O5, BaCO3, and CuO between 10 min and 1 h, and finally transition to the formation of Y2BaCuO5, BaCO3, and CuO at longer times. The absence of dispersion in impedance measurements as a function of frequency together with the gradual decay of conductivity (roughly corresponding to the remaining volume fraction of YBa2Cu3O7-x) indicates that not all grain boundaries are involved in the decomposition process.