Development and characterization of surface coated YB-123 conductors by a non-vacuum sol-gel technique

DEVELOPMENT AND CHARACTERIZATION OF SURFACE COATED YB- 123 CONDUCTORS BY A NON-VACUUM SOL-GEL TECHNIQUE (Ph. D. Thesis) Hasan OKUYUCU GAZİ UNIVERSITY INSTITUTE OF SCIENCE AND TECHNOLOGY November 2002 ABSTRACT Surface coated YbBa2CuaQ/ superconductor was produced by a non- vacuum soi-ge! technique and it was characterized. Ni tape, which was used as substrate, was annealed at temperatures between 800 °C- 1060 °C for different times in reducing atmosphere to get texture. Then Ni tape was characterized by means of ESEM, XRD, Pole Figure, AFM and Optical microscopy. To prevent Ni reaction with Yb-123 and to transfer tiie texture from Ni tape to superconducting layer, Gd203 buffer layer was coated on Ni tape by using a non-vacuum sol-gel technique. By means of ESEM, XRD, Pole Figure and AFM, Gd2Q3 buffer layer was found homogenous, pinhole and crack free and textured. Effects of number of dipping, annealing time and temperature on buffer layer texture were experimented. Superconducting Yb-123 layer was also coated by using a non-vacuum sol-gel technique. Four-point measurement was carried out to check tiie superconducting transition temperature. Critical transition temperature was found as 77 K and makes the operation in liquid nitrogen. Superconducting films were scanned by means ©f XRD 26 and film were found to be partially textured. Science Code : 604.01.01 Key words : Superconductor, Texture, Sol-Gel, Yb-123 Page number : 133 Adviser : Prof. Dr. İshak KARAKAYA