Structural and compositional characterization of rubidium-containing crystals of the Tl–Ba–Ca–Cu–O superconductors

Abstract

Large single crystals of the Tl–Ba–Ca–Cu–O superconductors have been grown from fluxes including up to 30 mol% Rb of the amount of Tl employed. Various phases have been grown with lattice parameters and superconducting properties similar to crystals grown previously without Rb, though the present crystal plates are usually larger and thicker. There is an increased likelihood of syntactic polycrystal growth as Rb content increases. Successive ion milling combined with energy dispersive X-ray analysis, EDAX, has shown that the Rb is uniformly distributed throughout the plates that are single phase crystals. Precession photographs show sharp diffraction patterns of quality comparable to our Rb-free plates. Magnetically determined Meissner T c values and transition widths are not significantly altered by Rb substitution. Single crystal X-ray structure refinements have been carried out on several single crystals of each of the four principal phases. In addition various crystal plates have been characterized and studied by transmission electron imaging.