Decomposition of YBa2Cu3O7−x during annealing in CO2/O2 mixtures

Abstract
The stability of YBa2Cu3O7−x superconductors toward reactions with CO2 in CO2/O2 gas mixtures has been studied during annealing at temperatures ranging from 600°C to 950°C. The results show that there are three different types of the reactions. The reaction products of these reactions all include BaCO3 and CuO, while the third product is dependent on the annealing temperature. At 600°C, YBa-carbonates were formed while Y2Cu2O5 and Y2BaCuO5 were formed at 815°C and 950°C, respectively. Transmission Electron Microscopy images show that the reactions started at grain boundaries with the formation of island-type precipitates.