THERMOANALYTICAL INVESTIGATIONS ON THE SOL-GEL SYNTHESIS OF YBA2CU3O7-DELTA

The high temperature superconducting compound YBa2Cu3O7-delta (Y-123) is synthesised by sol-ger process using various precursors viz., aceta te, acetate-citrate, nitrate-citrate and acrylamide. The phase purity of the final product depends on the homogeneity of the gels which inte rn depends on the bonding of the metal ions in the gels. The samples p repared by acrylamide and nitrate-citrate gel routes yielded phase pur e Y-123 compound with better superconducting properties. The mechanism of formation of Y-123 in ail these four gel routes is established by characterising the gels and intermediate phases using TG, DTA and XRD techniques. Kinetic analysis is carried out on the mass loss data usin g the method proposed by Phadni's and Deshpande. Avrami-Erofeev nuclei growth in case of acrylamide, diffusion controlled process in nitrate -citrate and phase boundary reaction mechanisms in case of acetate-cit rate gels are found to be responsible for the formation of Y-123 phase .