Non-oxidative and oxidative chlorination of (Bi,Pb)2Sr2Ca2Cu3Oy

The influence of oxidative and non-oxidative chlorination on the chemical and superconducting properties of (Bi,Pb)2Sr2Ca2Cu3Oy is studied on samples with different initial O content. Owing to oxidative chlorination of O-deficient phases a significant increase of Tc is observed although insulating, hygroscopic halide phases are formed and indications for the incorporation of Cl into the structure are not found. Obviously, reactive O is formed during degradation of the 2223 phase on the solid-gas phase boundary. The released O partially occupies anion vacancies in the unreacted O-deficient material resulting in improved intragranular superconducting behaviour. The reaction pathways of the heterogeneous solid-gas reaction are discussed on the basis of the results of chemical analysis.