Microstructure of the superconducting phase (85K) in the Bi-Sr-Ca-Cu-O System
The discovery of high temperature superconductivity by Bednorz and Muller in a cuprate-based system generated an extensive search for new superconducting oxide phases. Superconductivity at 90K was observed by Wu et al. in the Y-Ba-Cu-O system and this temperature, until recently, had not been exceeded reproducibly. Superconductivity at 20K was reported in another cuprate system containing bismuth instead of yttrium, and recently superconductivity at 85K and 110K was reported by Maeda et al. in a Bi-Sr-Ca-Cu-O system. A Bi2Sr2CaCu2O8.2 phase has been found to be the origin of the 85K superconducting transition, and its crystal structure was determined by x-ray diffraction. In this paper, we comment on the microstructure and chemistry of the new superconducting phase using selected-area electron diffraction (SAED), convergent beam electron diffraction (CBED), and x-ray energy dispersive spectroscopy (EDS) experiments.The superconducting Bi2Sr2CaCu2O8+x samples investigated were synthesized in air by standard solid-state reaction techniques from appropriate amounts of Bi2O3, CuO, SrCO3, and CaCO3.