Observation of curious spiral growth features in Tl doped Hg bearing high temperature superconducting tapes

Synthesis of Hg(Tl)Ba2Ca2Cu3O8+delta superconducting tapes have been accomp lished by annealing the precursor tape, Ba2Ca2Cu3Oy, (fabricated by doctor blade tape casting technique) in an environment of Hg(Tl) vapour. Character ization of superconducting HTSC tape sample was carried out through XRD, TE M, SEM and R-T measurements. Surface morphological investigations of the as -synthesized Hg(Tl)Ba2Ca2Cu3O8+delta HTSC tapes by scanning electron micros cope have shown the occurrence of curious growth characteristics resembling spiral like features. These growth spirals encompass nearly the whole grai n suggesting that spiral growth led to the formation of small crystal like grains of superconducting material Hg(Tl)Ba2Ca2Cu3O8+delta. The likely mech anism for the generation of these screw dislocations has been elucidated in terms of incoherent coalescence of growth fronts formed from Hg(Tl): 1223 and Hg(Tl): 1234 nuclei.