PHYSICOCHEMICAL CHARACTERIZATION OF SUPERCONDUCTORS FROM GEL STATE TO YBA2CU3O7-X FINAL PRODUCT

In the sol-gel method, the alkoxide precursor leads to the formation of YBCO (YBa2Cu3O7-x) oxide at a lower temperature than the acetate precursor, 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 measurement. Furthermore, the XPS measurement clearly shows that during the formation of YBCO oxide and the annealing of the samples, a new bond located at 527.5 eV appears. The literature, the result obtained by XPS on samples annealed for various times and the determination of the oxidation state of copper by iodometric titration confirm that this band, located at 527.5 eV, is characteristic of the YBCO orthorhombic structure formation.