ON PREVENTING THE DEGRADATION IN YBA2CU3O7-DELTA SUPERCONDUCTORS CAUSED BY GAMMA-IRRADIATION

The stability of high-T(c) YBa2Cu3O7-delta uncoated and coated with po lymers viz. polymethyl methacrylate (PPMA), polyvinyl chloride (PVC) a nd polystyrene (PS) bulk samples irradiated by gamma-rays of doses 3.0 24 x 10(5) and 1.210 x 10(6) rad (r) was investigated. The degradation was estimated by the change in critical temperature (T(c)), thermogra vimetric analysis (TGA) and oxygen content measurements. The activatio n energy was also determined to study the mechanism of degradation. Th e decrease in T(c) (DELTAT) was found to be different for samples coat ed with different materials. The results indicate that polymer coating s prevent degradation of the HTc superconductors. Though the extent of degradation depends on the nature of the polymer, plasma polymerized PMMA coating is found to be most effective in preventing the degradati on of YBCO.