Stability of superconducting YBa2Cu3O7 in the presence of water

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Abstract
The new high transition temperature superconductors such as YBa2Cu3O7 in powdered form have been observed to react vigorously at room temperature with water producing a nonsuperconducting cuprate with copper in oxidation state +2, O2, CuO, and Ba(OH)2. Similar reactions will probably occur with nearly equal rapidity in all cuprate superconductors. We have used room‐temperature and liquid N2 resistance measurements to study the stability of smaller surface area specimens (thin sheets). We have found that such specimens react slowly with humid air at room temperature and rapidly in air at 85 °C and 85% rel. humidity, the standard conditions used for accelerated humidity testing. The resultant end products are nonsuperconducting phases formed in from hours to days, depending on conditions. Furthermore, we have found that, while a plastic encapsulant considerably slowed such reactions, it did not eliminate them. The implications for both scientific experiments to characterize high transition temperature superconductors and for applications as well as possible remedies are discussed.