Ag-2223 (Bi) tapes structure and superconducting properties in dependence of initial powder type

An investigation was carried out into the critical properties and specific features of structure in composite tapes with a core material of composition 2:2:2:3.2 in bismuth system produced by freeze drying technique and taken at different stages of the synthesis process. Consideration is given to powder behavior in the process of cold drawing and rolling of composite tapes followed by heat treatment under similar condition as well as to evolution of microstructure, specificity of texture and kinetics of superconducting phase formation. It is shown that the most favorable type of structure in heat treated superconductors develops when core material powder is used in the form of a precursor consisting of fine mixture of dioxides and ''2212'' phase resultant from calcination within the interval 750--800 C. The critical current density more than 104 A/cm2 at 77 K was achieved in the composite tapes. The results of testing for small coils are presented