Upadhyayula V Varadaraju

The oxygen-deficient phase of the high T c superconductor, YBa2Cu3O7, was oxygen-enriched using the fluidization technique to give good superconducting properties. The normal method of oxygen treatment at 900°C for 24 h and at 600°C for 24 h has been reduced to just one treatment at 600°C for 12 h by the fluidization technique to achieve almost the same strength of superconducting signal for the YBa2Cu3O7 powder, which establishes the attractiveness of the latter route for the large-scale preparation of superconducting material. The particle sizes were in the range 0-90, 90-180 and 180-420 μm. The fluidized particles were crystalline with orthorhombic distortion. T c onset, estimated using the a.c. magnetic susceptibility method, was 91·3 K. The volume fraction of superconducting material in the product was 83·7-85·3%, one of the highest values reported so far for YBa2Cu3O7. © 1989 Indian Academy of Sciences.

The effect of oxide additives-CuO, SiO2, Y2O3, Bi2O3 and ZnO in 1-10 mol% on the sintering and superconducting properties of YBa2Cu3O7 was studied. SEM studies indicated improvement of grain size and interconnectivity due to the additives, the best results being obtained with Bi2O3, SiO2 and Y2O3. The superconducting transition temperature is unaffected (92±2 K) even with 10 mol % of the additives. ZnO, however, decreases the T c as expected. © 1989 Indian Academy of Sciences.