Effect of metal oxides on BiSrCaCuO glass ceramic superconductors

We report on the fabrication, electrical and optical properties of ceramic Bi/sub 2-x/M/sub x/Sr/sub 2/Ca/sub 2/Cu/sub 3/O/sub y/ (here M=Al and Ni and X=0.3) superconductors. The resistivity measurement revealed that as the Al is partially substituted at the Bismuth site in the BiSrCaCuO compound, it exhibited a T/sub c/ of 77k while the nickel substituted compound showed a T/sub c/ of 70k as compared to the undoped BiSrCaCuO compound having T/sub c/ of 851K. The infrared measurements in the range of 100-4000 cm-1 showed that the reflectance from the ceramic samples reduces as Bismuth is partially replaced by lighter elements such as Aluminum and Nickel. The observed phonon modes in the infrared conductivity spectra obtain form the Kramer-Kroning analysis shows a reduced strength of the most of phonon modes, even some of the vibrational features are completely smeared out. Furthermore some of the modes are observed to shift slightly in the frequency on doping, the change in the Tc and vibrational modes in attributed to destabilization of 2223 Phase, and it appears that the system in an over doped region for 0.3 mol concentration of Al and Ni where T/sub c/ is normally reduced. (author)