INTERACTION OF PYRIDINE WITH Bi₂CaSr₂Cu₂O_x

Abstract
The adsorption of of pyridine on single crystals of Bi₂CaSr₂Cu₂O_x has been followed by optical microscopy on the crystal surface, where a blue solution is formed as a first step of reaction. The superconducting properties of the single crystal and its structure were monitored by ac susceptibility and by x-ray diffraction measurements. The results (as observed by the growth of the blue solution boundary versus time with D_aa = 3.7x10^-10 cm²/s.) indicate that the reaction starts at nucleation sites on the basal surface of the crystal. The edges of the crystal also show blue nucleation sites but these do not grow with time. The changes in the ac susceptibility indicate that the superconducting volume has increased. This can be explained by the intercalation of pyridine, although the x-ray data are not very conclusive.