Manufacture of 2nd generation high-temperature superconducting tapes with a green processing technology

This thesis presents the preparation of REB_a2Cu₃O_7-x (REBCO, RE = rare earth) superconducting films on single crystal substrates using fluorine-free chemical solution deposition (CSD) method. All my work consists of five subjects described as follows:

1) The effects of annealing temperature on texture and morphology of YBCO superconducting films on (100) LaAlO₃ single crystal substrates derived from a water based sol-gel process were investigated. J_c of YBCO film reaches 1.7MA/cm² at 77K and 0 T (Chapter 3);
2) The influence of water vapor content during pyrolysis process on preparation of YBCO films form water-based sol-gel was investigated (Chapter 4);
3) Phase evolution of precursors from water-based sol-gel has been systematically studied using conventional XRD, in-situ synchrotron XRD, TG-DTG analysis, FTIR spectrometer (chapter 5);
4) GdBCO propionic acid-base precursor solution was prepared and thermal decomposition of this precursor was studied. GdBCO film with J_c =1.33 MA/cm² at 77K were epitaxially grown on (100) LaAlO3 single crystal substrates by means of propionic acid based solution (chapter 6);
5) The thermal decomposition of Nd(C₂H₅CO₂)₃·H₂O has been investigated using TG, DTA analysis, infrared spectroscopy and X-ray diffraction. A comparison of thermal property of Nd propionate in Ar and that in air was represented as well (chapter 7).

These results explored the processing conditions, such as annealing temperature and water vapor, are investigated with regard to their influences on texture, morphology and superconducting property of films. Superconducting performance of films prepared from both fluorine-free approaches under optimal conditions gives a promising application in fabrication of coated conductor tapes with long length. The phase evolution of precursors was also investigated as well.