Correlation of the electric field effect with the weak link behaviour in granular YBCO superconductors

The effect of an electric field E = 120 MV m-1 on the critical current Ic and the current-voltage characteristics of yttrium-based high-Tc ceramics have been studied experimentally with data on the electric field effect related to the critical current behaviour with temperature near the critical temperature Tc. The objects of study were ceramics with stoichiometric composition YBa2Cu3Oy, fabricated in different sintering conditions (123-I and 123-II samples), copper-deficient YBa2Cu3-xOy (D samples) and YBa2Cu3-xOy/Agx ceramics (S samples with silver present in amount equal to the copper deficiency 0Ic, whereas in S and 123-II samples no field effect is observed. The results of the measurements of the temperature dependence of Ic near the critical temperature confirmed the presence of (author) value, the force has reached its maximintergrain junctions (SIS) in D and 123-I samples, and superconductor-normal metal-superconductor proximity junctions (SNS) in S and 123-II samples. The conclusion is drawn that the electric-field effect correlates with the existence of SIS-type weak links at grain boundaries in the ceramic. (author)