NONOXIDATIVE AND OXIDATIVE CHLORINATION OF (BI, PB)2SR2CA2CU3OY

The influence of oxidative and non-oxidative chlorination on the chemi cal and superconducting properties of (Bi, Pb)2Sr2Ca2Cu3Oy is studied on samples with different initial 0 content. Owing to oxidative chlori nation of O-deficient phases a significant increase of T(c) is observe d although insulating, hygroscopic halide phases are formed and indica tions for the incorporation of Cl into the structure are not found. Ob viously, reactive 0 is formed during degradation of the 2223 phase on the solid-gas phase boundary. The released 0 partially occupies anion vacancies in the unreacted 0-deficient material resulting in improved intragranular superconducting behaviour. The reaction pathways of the heterogeneous solid-gas reaction are discussed on the basis of the res ults of chemical analysis.