HIGH-T-C SUPERCONDUCTING BI(AL)-CA-SR-CU-O GLASS-CERAMIC FIBERS DRAWNFROM GLASS PREFORMS

Bi(Al)-Ca-Sr-Cu-O glass-ceramic fibres over 100 cm in length were succ essfully drawn from a glass preform above the crystallization temperat ure, T-x. The diameters of the uniformly drawn fibres with circular cr oss-section could be controlled in the range from 25-200 mu m and the drawing speed was as high as 200 cm min(-1). In this work Al2O3 was us ed to modify the properties of the glass. It increased the glass trans ition and crystallization temperatures but did not significantly incre ase the glass working range. Shrinkage and increase of density during heat treatment of the glass fibres were observed. The annealed (825 de grees C/12 h in air) Bi4Al0.1Ca3Sr3Cu4Oy glass-ceramic fibre showed a T-c(onset) of 82 K and a T-c(zero) of 71 K.