Oxygen vacancies ordering in the Ba sub 2 YCu sub 3 O sub (7-x) (O<=x<=1) Superconducting System.

Diffuse scattering streaks or bands have been observed in electron diffraction photographs for samples belonging to the superconducting system Ba sub 2 YCu sub 3 O sub (7-x). (O=x=1). In-situ experiments show that this diffuse scattering can be associated with short range ordering of oxygen vacancies. The same vacancy- ordering occurs in previously reduced samples. Three types of diffuse scattering are observed, each corresponding to a short-range-order scheme.