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

The stability of high-T(c) YBa2Cu3O7-delta uncoated and coated with polymers viz. polymethyl methacrylate (PPMA), polyvinyl chloride (PVC) and polystyrene (PS) bulk samples irradiated by gamma-rays of doses 3.024 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)), thermogravimetric analysis (TGA) and oxygen content measurements. The activation energy was also determined to study the mechanism of degradation. The decrease in T(c) (DELTAT) was found to be different for samples coated with different materials. The results indicate that polymer coatings 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 degradation of YBCO.