Oxygen excess in Bi-2212: study of a Pb-substituted compound

Abstract A systematic quantitative investigation of oxygen excess in polycrystalline Bi 1.8 Pb 0.2 Sr 2 CaCu 2 O 8+ δ as a function of temperature and oxygen partial pressure ( P O 2 ) has been achieved. It is shown that the absolute oxygen content is slightly lower than in the lead-free compound, varying within a range of same magnitude when ( T , P O 2 ) conditions are changed. Despite the overall thermodynamic behaviour is comparable to those of other Bi-based cuprates, (Bi,Pb)-2212 appears less stable due to its facility in forming secondary phase or evaporating lead. According to T c measurements on samples displaying precisely controlled oxygen concentrations, Bi/Pb substitution does not induce significant overdoping. Charge compensation is thus confirmed to occur preferentially through oxygen loss and creation of holes out of the Cu–O planes.