Ad. Nikulin et al., AG-2223 (BI) TAPES STRUCTURE AND SUPERCONDUCTING PROPERTIES IN DEPENDENCE OF INITIAL POWDER TYPE, IEEE transactions on magnetics, 30(4), 1994, pp. 2368-2371
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.