Growth of heavily Pb-substituted Bi-2201 single crystals by a floating zone method (SOLID STATE CHEMISTRY-Artificial Lattice Compounds)

Abstract

Single crystals of the heavily Pb-substituted Bi-2201 phase were grown to a typical planar shape of 6 x 3 x 0.03 mm3 by using a floating zone method [1]. These crystals with the highest Pb content ever reported are free from any structural modulation as examined by transmission electron microscopy, and the orthorhombic lattice parameters are a = 5.300(3) A, b = 5.392(3) A, and c = 24.603(5) A (V = 703.2 A3). Their superconducting properties can be modified within the over-doped region in such a way that the transition temperature, Tc, is raised from 3 K for the as-grown crystals to 23 K by annealing at 550 °C for 2 weeks in a vacuum of ~10-4 Pa. The out-of-plane resistivity of the as-grown crystals remains metallic down to 20 K, while it becomes semiconductive below 160 K after the annealing.