Preparation of c-Axis-Oriented NdBa2Cu3O7-.DELTA. Thin Films by a Sol-Gel Method with Alkoxide and Hydroxide Solutions

Superconducting NdBa2Cu3O7-δ (Nd123) thin films were prepared by a sol-gel method. Nd and Ba-alkoxides and Cu(OH)2 were used as metal sources, and isopropanol and dimethylaminoethanol were used as solvents. Sols were spin-coated on polycrystalline Ag metal substrates, dried at 80°C and finally heated at 800°C, resulting in the formation of single-phase Nd123. The films exhibited preferred orientation along the c-axis after coating two times. However, the orientation was disturbed when the number of coatings increased. This behavior is attributable to the interfacial reaction between the film and the substrate to form liquid phases and/or structural relaxation of the gel film upon heating. Superconducting transition was observed at 90K after annealing the films in O2 with superconducting quantum interference device (SQUID) measurements.