Synthesis and characterization of Er-substituted Bi-2223 H-Tc glass-ceramic superconductors

The Bi2Sr2Ca2Cu3-xErxO10+delta (x = 0.5 and 1.0) H-T-c system was prepared by glass-ceramic technique to investigate the microstructural formation. thermal and transport properties. We have found that Er+3 ions have a solid solubility limit in the Bi-2223 system and this limit was passed at x = 1.0. Below this limit glass samples were prepared and converted to the glass-ceramic form easily, but after the solid solubility limit glass formation was diminished and crystallized samples were formed after melt quenching. The substitution had considerable effect on the electrical properties comparing with the unsubstituted Bi-2223 material. The T-c values of the x = 0.5 and 1.0 sample were found to be 71 +/- 0.1 K. The thermoelectric power data were analyzed in view of two band model with linear T-term and Xin's two band model. Thermoelectric power was obtained to be positive for the both samples, indicating that the hole type conductivity is dominant in the materials prepared. The magnitude of thermal conductivity, kappa, was also influenced by the Er concentration. When the Er concentration was increased the magnitude of kappa was suppressed. It strongly indicates that the impurities play a significant role in limiting the heat transport due to a strong increase of the electron-phonon-impurity scattering rate. (C) 2004 Elsevier B.V. All rights reserved.