Qualitative study on the reaction of Bi1.8Pb0.4Ca2Sr2Cu3Oy superconductor with water

Article abstract of DOI:10.1016/0921-4534(93)90125-A

When Bi_1.8Pb_0.4Ca₂Sr₂Cu₃O_y powders were immersed into deionized water, a large quantity of Ca²⁺ and Sr²⁺ ions was detected in the aqueous solution, indicating the decomposition of the Bi_1.8Pb_0.4Ca₂Sr₂Cu₃O_y superconductors in water. The pH of the solution was initially increased rapidly to 11.1 due to the formation of OH^- ions. However, after 30 min, in the open system, the Ca²⁺ and Sr²⁺ ions would further react with CO₂ in the atmosphere to form sparingly soluble carbonates and the pH of the solution was slowly decreased to 9.81 over 20 h. Only a small amount of Bi³⁺, Pb²⁺ and Cu²⁺ ions was detected in the aqueous solution. Non-soluble products, such as Bi₂CuO₄, CuO and Cu₆PbO₈, were observed in the reaction residue which might act as a barrier to prevent deterioration of the superconductor with water in the bulk sample. The chemical equation was given as Bi_1.8Pb_xCa₂Sr₂Cu₃O_y(s) + 4H₂O → 2Ca_(aq)²⁺ + 2Sr_(aq)²⁺ + 8OH_(aq)^- + 0.9Bi₂CuO_4(s) + xCu₆PbO_8(s) + (3-0.9-6x)CuO_(s).