VARIATION OF THE LATTICE-PARAMETERS OF A BI-BASED SUPERCONDUCTOR WITHTEMPERATURE

Variation of the lattice parameters and thermal expansion coefficients of Bi-2223 superconductor have been measured from room temperature up to the melting point using X-ray diffraction. The lattice parameters (a and c) gradually increase up to about 250 degrees C. Between 250 de grees C to 450 degrees C the variation of the lattice parameters are q uite anomalous, in that a remains almost constant while c decreases. F rom 450 degrees C to 600 degrees C both parameters gradually increase. Above 650 degrees C the structure of Bi-2223 becomes unstable. The in itial thermal expansion coefficient along the c-axis is about four tim es that along the a-axis. Similar large anisotropy has also been obser ved in the measurements of the stress of Bi-2223.