Investigations of photo-induced changes in the superconducting ceramic were carried out. The changes were produced by using a CO2 laser (10.6, 12W/cm2). Anomalous changes in voids were caused by laser exposure times of about 180s, together with marked changes in resistivity. The results were explained in terms of the clustering of O vacancies in Cu-O chains under illumination.

I.V.Kityk, J.Kasperczyk, R.V.Lutciv, M.Sanchez: Solid State Communications, 1996, 98[6], 587-90