AG-2223 (BI) TAPES STRUCTURE AND SUPERCONDUCTING PROPERTIES IN DEPENDENCE OF INITIAL POWDER TYPE

Investigation was carried out into the critical properties and specifi c features of structure in composite tapes with a core material of com position 2:2:2:3.2 in bismuth system produced by freeze drying techniq ue and taken at different stages of the synthesis process. Considerati on is given to powder behaviour in the process of cold drawing and rol ling of composite tapes followed by heat treatment under similar condi tion as well as to evolution of microstructure, specificity of texture and kinetics of superconducting phase formation. It is shown that the most favourable type of structure in heat treated superconductors dev elops when core material powder is used in the form of a precursor con sisting of fine mixture of dioxides and ''2212'' phase resultant from calcination within the interval 750-800-degrees-C. The critical curren t density more than 10(4) A/cm2 at 77 K was achieved in the composite tapes . The results of testing for small coils are presented.