ADSORPTION AT GRAIN-BOUNDARIES AND SUPERC ONDUCTING PARAMETERS OF CERAMICS

The influence of inert molecule adsorption at the grain boundaries on critical temperature T(c) , critical current I(c) and first critical f ield H(jc1) of different HTSC ceramics is investigated. It is shown th at the critical parameters of the ceramics Bi1,8Pb0,2Sr2Ca2Cu3Oy and Y Ba2Cu3O7-delta are sensitive to exposure time in gaseous nitrogen at l ow temperature. Similar results are obtained, using chemically inert b enzole. The most environment sensitive critical parameter is I(c), and its behaviour is defined by the mean grain size in the ceramics. Some possible mechanisms of the effect are discussed as well as possible t roubles, which may appear in technical application of HTSC ceramics.