Growth and characterization of BiSrCaCuO superconducting fibers

Abstract With the laser-heated floating zone method, fibers of nominal overall composition Bi 2 Sr 2 CaCu 2 O 8±Z and Bi 2 Sr 2 Ca 2 Cu 3 O 10±Z have been grown. Fibers of uniform diameter up to ∼1 cm long have been produced. The influence of the growth rates and feed rod compositions on the microstructure of grown fibers were determined with XRD, SEM, EDS, and resistive T c measurements. At 5 mm/h growth rate, compositionally homogeneous material can be grown from the 2212 composition over a length of several hundred μm. Fibers grown at higher rates consist predominantly of Bi 2+x (Sr,Ca) 2−X CuO 6±Z (the 25Ȧ phase) with smaller amounts of Bi 2 (Sr,Ca) 3 Cu 2 O 8±Z (the 31Ȧ phase) and (Sr,Ca)CuO 2 phases. These multiphase fibers show a resistive superconducting transition at 80K. After annealing at 800°C for 12 hrs in air, the proportion of the 31Ȧ phase is increased, the normal state resistivity is decreased, and the T c rises to 90K.