K. Brzezinska et al., EFFECT OF CARBON-DIOXIDE ON THE REACTION OF YBA2CU3O6.5-VAPOR(X WITH WATER), Journal of Materials Science, 28(19), 1993, pp. 5155-5160
The influence of carbon dioxide on the reaction between YBa2Cu3O6.5+x
powder and air saturated with water vapour was studied. Superconductor
powder samples were exposed to air that was saturated with water vapo
ur which (a) was free of CO2, (b) was saturated with CO2, and (c) cont
ained ambient levels of CO2. In another experiment, the effect of pure
, dry CO2 (1 atmosphere partial pressure) was studied. The time variat
ions of sample weight, oxygen content and X-ray diffraction (XRD) spec
trum were determined. In water-saturated air, the rate of decrease of
the oxygen content in YBa2Cu3O6.5+x decreased with increasing partial
pressure of CO2. XRD was used to identify the reaction products. Highe
r partial pressures of CO2 favour the formation of a barrier layer (Ba
CO3) which inhibits the reaction of the underlying YBa2Cu3O6.5+x with
water vapour. Very little decrease in oxygen content occurred on expos
ure of YBa2Cu3O6.5+x to pure, dry CO2.