Stability of Bi2Sr2Ca1Cu2O8 ±δ Thick Films at Elevated Oxygen Pressures and Temperatures

Bi₂Sr₂Ca₂Cu₂O_8±δ-type compound thick films were exposed to oxygen-argon-gas mixtures (1% to 20% oxygen gas) at elevated pressures (up to 207 MPa) and temperatures (500° to 940°C) for times ranging from 5 to 96 h. At a sufficiently high oxygen fugacity and temperature, Bi₂Sr₂Ca₁Cu₂O_8±δ decomposed via a solid-state reaction. Room-temperature X-ray diffractometry and electron probe microanalysis of decomposed films revealed the presence of Bi₂(Sr,Ca)₂-Cu₁O_6±θ ro-type compound, Bi₂Sr₂,Ca₁O_8±δ-type compound, and CuO. Bi₂Sr₂Ca₁Cu₂O_8±δ decomposition was accompanied by a modest weight gain, which was consistent with an oxidation reaction. The solid-state decomposition reaction could be reversed by heat treatment of decomposed films at 860°C in pure, flowing oxygen at ambient pressure.