GROWTH OF HEAVILY PB-SUBSTITUTED BI-2201 SINGLE-CRYSTALS BY A FLOATING-ZONE METHOD

Single crystals of the heavily Pb-substituted Bi-2201 phase with a com position of Bi1.80Pb0.38Sr2.01CuO6+delta as determined by fluorescence X-ray composition analysis were grown to a typical planar shape of 6 x 3 x 0.03 mm(3) by using a floating zone method, These crystals with the highest Pb content ever reported are free from any structural modu lation as examined by transmission electron microscopy, and the orthor hombic lattice parameters are a = 5.300(3) Angstrom, b = 5.392(3) Angs trom, and c = 24.603(5) Angstrom (V = 703.2 Angstrom(3)). Their superc onducting properties can be modified within the over-doped region in s uch a way that the transition temperature, T-c, is raised from 3 K for the as-grown crystals to 23 K by annealing at 550 degrees C for 2 wee ks in a vacuum of similar to 10(-4) Pa. The out-of-plane resistivity o f the as-grown crystals remains metallic down to 20 K, while it become s semiconductive below 160 K after the annealing. (C) 1997 Elsevier Sc ience B.V.