| dc.description |
The effect of an electric field E = 120 MV m<sup>-1</sup> on the critical current I<sub>c</sub> and the current-voltage characteristics of yttrium-based high-T<sub>c</sub> ceramics have been studied experimentally with data on the electric field effect related to the critical current behaviour with temperature near the critical temperature T<sub>c</sub>. The objects of study were ceramics with stoichiometric composition YBa<sub>2</sub>Cu<sub>3</sub>O<sub>y</sub>, fabricated in different sintering conditions (123-I and 123-II samples), copper-deficient YBa<sub>2</sub>Cu<sub>3-x</sub>O<sub>y</sub> (D samples) and YBa<sub>2</sub>Cu<sub>3-x</sub>O<sub>y</sub>/Ag<sub>x</sub> ceramics (S samples with silver present in amount equal to the copper deficiency 0<x0.4). In D and 123-I samples studied at 77 K, the applied electric field increases I<sub>c</sub> and reduces substantially the resistivity at I>I<sub>c</sub>, whereas in S and 123-II samples no field effect is observed. The results of the measurements of the temperature dependence of I<sub>c</sub> near the critical temperature confirmed the presence of superconductor-insulator-superconductor tunnel intergrain 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. |
