The influence of a gaseous annealing atmosphere on the structure and properties of Bi2Sr2CaCu2O8+δ and Bi1.8Pb0.2Sr2CaCu2O8+δ compounds

In the present work, we have studied the influence of reducing and neutral atmospheres, vapors of water and simple organic compounds of various classes on the structure and properties of high-temperature superconductive (HTSC) Bi2Sr2CaCu2O8+δ (2212) and Bi1.8Pb0.2Sr2CaCu2O8+δ (Pb-2212) compounds in the temperature range of 150 – 700°C. It has been shown that treatment in an argon atmosphere at 700°C leads to an increase in the critical temperature (Tc) of Bi1.8Pb0.2Sr2CaCu2O8+δ to 99 K. Moreover, the oxygen index for this compound is close to the stoichiometric value (≈8.03). At 150°C in a reducing atmosphere, hydrogen weakly intercalates into the 2212‑structrure. In the process, no obvious signs of copper, bismuth and lead reduction are observed, but a rise in Tc occurs. Bismuth ceramics involves no interaction with vapors of water and organics at 200°C. The interaction proceeds at t ≥ 300°C, and the 2212 compound decomposes under alcohols as a consequence of the reduction process, bringing about a cationic disordering. Vapors of toluene have a “mild” impact on both Bi2Sr2CaCu2O8+δ and Bi1.8Pb0.2Sr2CaCu2O8+δ ceramics, even at 400°C, gives rise to an elevation in Tc to 92 K and 94 K, respectively. The ability of 2212 compounds to act as a catalyst when interacting with organic compounds has been discovered.