THE EFFECT OF PROCESSING PARAMETERS ON THE ENVIRONMENTAL STABILITY OF YBACUO SUPERCONDUCTOR

The effect of processing parameters on the environmental stability of YBaCuO superconductor was studied by exposing the pellets to a constant level of relative humidity for periods up to 2000 h. Various annealing treatments and compaction pressures, including hot pressing, were utilized to fabricate the pellets. T(c) measurements, Auger electron spectroscopy, energy-dispersive X-ray analysis, scanning electron and optical microscopy were employed to characterize the degradation. Samples coated with a polyimide material were also included in the study to determine its utility as a moisture barrier. Results indicated that a slow anneal (41 h) in flowing oxygen produces samples that are far more stable compared to the ones annealed rapidly (9 h) in air. The pellet compaction pressure does not appear to significantly affect the degradation characteristics of the material. The hot-pressed samples showed considerable degradation within 800 h of exposure. The polyimide was found to be ineffective in inhibiting the attack of the humid environment.