Research On Epitaxial Process And Sm³⁺Doping Effect Of Ybco Thin Films

YBCO thin films prepared by chemical solution deposition, and the effect of sintered process on films" structure and properties been investigated. According to the results, two temperatures ranges suitable for film epitaxial growth had been obtained in this paper. And the low epitaxial temperature range had been optimized. Sm3+doping effects YBCO thin-film which prepared by low epitaxial temperature had been studied.In chapter1, the knowledge of superconductivity had been introduced, including the development of superconducting materials, superconductivity theory, and the structure of high-temperature superconducting materials, the coated conductor and their preparation methods.In chapter2, the experimental methods and characterization tools involved in this paper had been described. X-ray diffraction, scanning electron microscopy, and PPMS were introduced in details.In chapter3, at first the composition of YBCO had been adjusted to ensure the surface quality; secondly YBCO thin films sintered at different temperature of758℃to772℃had been prepared and two temperatures ranges suitable for film epitaxial growth around760℃and770℃had been obtained; thirdly the epitaxy time of low epitaxial temperature ranges had been studied and30min was been proved to be the suitable epitaxy time for low epitaxial temperature ranges. The physics properties of YBCO prepared in low epitaxial temperature ranges showed good performance, the critical temperature Tc can reach90K and the critical current density Jc at77K in self-field can be over3MA/cm2.In chapter4, the reason of two different epitaxial temperature ranges and the mechanism about the epitaxial process were discussed. After induced nucleation occurred in the surface between YBCO films and LAO substrates, the nucleation and the epitaxy growth completed with each and leads to two different epitaxy ranges. Substrate-forming phase epitaxial mechanism was proved to be the mechanism about the epitaxial process of YBCO thin films.In chapter5, Sm3+doping effects on the structures, surface morphology and superconducting properties of YBCO thin-film have been studied. Doping effects of Sm3+in YBCO films have also been discussed and the result indicated the doping amount need to be optimized.