Adsorption on grain boundaries and superconducting parameters of ceramics

We studied the effect of adsorption of inert molecules on the critical temperature Tc, the critical current Ic, and the first critical field Hjc1 of various HTSC ceramics. The critical parameters of the Bi1.8Pb0.2Sr2Ca2Cu3Oy and YBa2Cu3O7−δ ceramics are shown to be sensitive to the time of keeping in nitrogen at low temperatures. Similar results have been obtained by making use of the chemically neutral benzene. The parameter that is most sensitive to the action of environment is Ic; its behavior is controlled by the grain size of the ceramic. We discuss a possible mechanism of this effect as well as possible difficulties that can be encountered in technical applications of the HTSC ceramics.