Effect of annealing on superconductivity of Pb-doped Bi-Sr-Ca-Cu-O single-crystal superconductors

Abstract
The microstructure of high quality Pb‐doped Bi2Sr2CaCu2Ox single crystals grown by the flux technique has been studied by transmission electron microscopy (TEM). The single crystals have a superconducting transition temperature (Tc) of about 90 K as grown; Tc drops to about 83 K after annealing in air at 600 °C. TEM results show that the as‐grown crystals exhibit twinning. The twin boundaries were found to be parallel to the (100) and (010) lattice planes. However, upon annealing the twin structure disappeared. This microstructure change is discussed in terms of a possible cause for the Tc decrease in the annealed crystals.