Gas adsorption and desorption characteristics of oxide superconducting powders.

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Abstract
Temperature programmed desorption (TPD) measurements in vacuum were examined for the oxide superconducting powders of synthesized high Tc Bi-Pb-Sr-Ca-Cu (Bi system) and YBa2Cu3O7-y (Y system). Oxygen desorption peak was observed around 470°C for the powder of Bi system after annealing at 400°C in oxygen atmosphere. Oxgen desorption peaks of Y system have been separated in four peaks. The desorption peak at 400-460°C is owing to the desorption of oxygen in "Cu(1) plane". Two desorption peaks at 650-670°C and at 790°C seem to originate from impurity phases. The desorption peak at 900°C arises from phase separation reaction.To estimate sensitivity to water and carbon dioxide of the powders of Bi and Y system, TPD measurements were carried out after exposure to water vapor or carbon dioxide. TPD spectra of Bi system show no remarkable difference from those after annealing in oxygen atmosphere. However, two water desorption peaks were observed for the powders of Y system after exposure to water vapor at room temperature, which suggests that chemical reaction have proceeded.

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