PHYSICOCHEMICAL CHARACTERIZATION OF SUPERCONDUCTORS FROM GEL STATE TOYBA2CU3O7-X FINAL PRODUCT

In the sol-gel method, the alkoxide precursor leads to the formation o f YBCO (YBa2Cu3O7-x) oxide at a lower temperature than the acetate pre cursor, regardless of the base used for adjustment of the pH, though a polymeric gel is obtained in each case. The principal reason for this behaviour is that the alkoxide precursor leads to the formation of a metalloxane bond during hydrolysis, during polycondensation and during the heat treatment. This information is principally obtained by XPS m easurement. Furthermore, the XPS measurement clearly shows that during the formation of YBCO oxide and the annealing of the samples, a new b ond located at 527.5 eV appears. The literature, the result obtained b y XPS on samples annealed for various times and the determination of t he oxidation state of copper by iodometric titration confirm that this band, located at 527.5 eV, is characteristic of the YBCO orthorhombic structure formation.