Preparation And Properties Of GdBa₂Cu₃O_7-δ/YBa₂Cu₃O_7-x Double-Layer Film

The Josephson junction with the structure of superconducting layer/middle layer/superconducting layer has the characteristics of magnetic field effect and microwave induction,which has important application value in the superconducting computer,medical NMR and other high sensitivity instruments.The application of HTS Josephson junction is greatly limited by the difficulty in preparing the ultrathin intermediate layer（serveral nanometers）.Therefore,it is urgent to choose an effective preparation method for the intermadiate layer of high temperature superconducting Josephson junction.In this paper,the sol-gel method is used to prepare the GdBa₂Cu₃O_7-δ/YBa₂Cu₃O_7-x double-layer superconducting thin film and its fine structure.It is expected that a lattice strain layer will be formed by the difference in lattice constant of the heterogeneous superconducting layer to serve as a high-temperature superconducting Josephson.The intermediate layer of the junction can realizes the Josephson effect,which can avoid the difficulty of preparing the ultra-thin intermediate layer in the traditional three-layer structure and simplify the preparation process of the superconducting Josephson junction.Carried out the following research work:（1）GdBCO heat treatment process was studied in the heat treatment temperature,heat treatment time,and the oxygen levels in the atmosphere affect GdBCO membrane phase.GdBCO photosensitized sol was prepared by adding benzoyl acetone（BzAcH）chemical modifier,and the mechanism of chelation between BzAcH and sol was analyzed,then the micron GdBCO lattice was prepared,and the GdBCO micrograph with Tc of 90K was obtained at 830℃.（2）The GdBCO/TFA-YBCO（low-Fluorine YBCO）and GdBCO/Fuorine-free YBCO double-layer films were prepared and finely atructured.The superconductivity of the two doublelayer films was tested and found that the resistance zero temperature of GdBCO/TFA-YBCO double-layer film is about 69K,the Tc of YBCO in the GdBCO/fluorine-free YBCO structure is 90K,and the Tc of GdBCO is 91K.Testing of the current-voltage（I-V）of the two structures found that the GdBCO/TFA-YBCO structure did not exhibit zero-voltage overcurrent.The GdBCO/fluorine-free YBCO double-layer structure current-voltage（I-V）test curve shows the zero-pressure superfluidic characteristics.The analysis suggests that because of the middle lattice strain layer acts as the middle layer of the Josephson junction,and the GdBCO/fluorine-free YBCO double-layer structure exhibits the SNS critical effect.