Research On Boron Doped YBCO Films By MOD Process

High temperature superconductors have good electrical properties and high Jc.They are used in weak and strong current system widely.Because of this,high temperature superconductors are focused by more and more people.YBa2Cu3O7-?(YBCO)is a kind of high temperature superconductor.The preparation methods of YBCO include TFA-MOD process.TFA-MOD process is easy to control the components.Its cost is low and easy to scale largely.In this dissertation,MOD process was used to prepare YBCO films on LaAlO3.The dissertation used Boron doping method to join the magnetic flux pinning.The structure and properties of the YBCO and Boron doped YBCO films with MOD process were systematically studied and contrasted.Meissner effect and the impact of Magnetic signals were systematically studied in liquid nitrogen temperature zone and normal temperature.At first,the preparation technology research of YBCO films were studied with MOD process on LaAlO3 and used Boron doping process to improve electrical properties.Copper acetate was replaced by Copper Octoate in order to optimize technical problems,such as precursor films cracking in heat treatment.The dissertation proposed one-step heat treatment on this basis.One-step process used Boron to increase viscosity of precursor solution and combine low temperature and high temperature treatment entirely.Using one-step method could save time and raise efficiency.Boric acid decomposed into boric oxide in high temperature and was doped in YBCO films to be a kind of defect to increase electrical performance in high magnetic field.After doping Boron,YBCO films had good inner texture and exterior orientation.The extent of c-axis orientation was high enough to form good YBCO crystal structure.Y.Ba,Cu and B were equally distributed in films.The ratio of the three elements amount of substance is 1:2:3.The grain fusion situation of Boron doped YBCO films was better than YBCO films and could form a more dense structure.The surface of the structure had less pore than YBCO films.Jc was improved from 0.465MA/cm2 to 0.673MA/cm2.Tc was improved from 85.72K to 89.27K.Then Meissner effect and the impact of magnetic signals were initially studied in liquid nitrogen temperature zone and normal temperature.When the situation was that field frequency was 30Hz,coil inductance was 1.65mH,the lock-in amplifier was used to judge the superconductivity of films.The research found that YBCO films don't have superconductivity in normal temperature.The superconducting samples had no effect on frequency and amplitude of the magnetic signal when the signal was sine wave.The phase position was changed by 90° in the effect of samples.The superconducting samples had no effect on frequency and amplitude of the magnetic signal when the signal was square wave.The square was changed into pulse wave.The phase position was changed by 90° in the effect of samples.The research found that YBCO films have superconductivity in liquid nitrogen temperature zone.The sine wave was changed into triangular wave.The frequency and amplitude was increased by films.The square wave was changed into pulse wave.The frequency was invariant.The amplitude was decreased by films.The phase position was changed by 180°in the effect of films.