Stabilisation of the 110 K phase in Pb-substituted Bi-Sr-Ca-Cu-O
B Jayaram; P C Lanchester; M T Weller; J R Grasmeder; P A J de Groot; G P Rapson; B Jayaram; Dept. of Phys., Southampton Univ., UK; P C Lanchester; Dept. of Phys., Southampton Univ., UK; M T Weller; Dept. of Phys., Southampton Univ., UK; J R Grasmeder; Dept. of Phys., Southampton Univ., UK; P A J de Groot; Dept. of Phys., Southampton Univ., UK; G P Rapson; Dept. of Phys., Southampton Univ., UK
Журнал:
Journal of Physics: Condensed Matter
Дата:
1989-01-16
Аннотация:
A number of samples of Bi<sub>2-x</sub>Pb<sub>x</sub>Sr<sub>2</sub>Ca<sub>3</sub>Cu<sub>4</sub>O<sub>y</sub> (0<or=x<or=0.8) have been prepared by solid state reaction. All major peaks in the powder diffraction spectra of samples with x=0.2 and 0.4 could be attributed to the Bi<sub>2</sub>Sr<sub>2</sub>Ca<sub>2</sub>Cu<sub>3</sub>O<sub>y</sub> phase with slight orthorhombic distortion. Resistivity measurements of these samples showed zero resistance at 100 K with onset of superconductivity around 110 K. The effect of variations of sintering and annealing have been studied in order to optimize conditions for obtaining the 110 K phase. From flux exclusion measurements the volume fraction of the high-T<sub>c</sub> phase is estimated to be around 40% at best. These studies tentatively indicate that Pb substitutes preferentially on the Ca site rather than the Bi site in the Bi-Sr-Ca-Cu-O lattice. Samples with x=0.0 and x>0.4 showed zero resistance around 70 K with no indication of a phase with a higher T<sub>c</sub>.
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