Crystallographic, thermodynamic, and transport properties of the Bi2Sr3-xCaxCu2O8+ delta superconductor.

Abstract

We have demonstrated the presence of a single-phase solid solution for the ${\mathrm{Bi}}_{2}{\mathrm{Sr}}_{3\ensuremath{-}x}{\mathrm{Ca}}_{x}{\mathrm{Cu}}_{2}{\mathrm{O}}_{8+\ensuremath{\delta}}$ superconductor, in the $1.25\ensuremath{\le}x\ensuremath{\le}2.0$ range. The lattice parameters and melting points vary monotonically with $x$, both increasing towards the Sr-rich composition. This monotonic variation of the lattice parameters extends into the $0.8\ensuremath{\le}x\ensuremath{\le}2.2$ range, but the material is multiphased outside the $1.25\ensuremath{\le}x\ensuremath{\le}2.0$ limit. Superconducting onsets in the ranges of 70-89 and 108-118 K have been obtained; however, the exact results are very sensitive to processing parameters. Magnetization measurements indicate high intragranular current densities (${J}_{c}$) at 5 K of \ensuremath{\sim}5\ifmmode\times\else\texttimes\fi{}${10}^{6}$ A/${\mathrm{cm}}^{2}$. The actual transport ${J}_{c}$ is low (\ensuremath{\cong} 70 A/${\mathrm{cm}}^{2}$ at 4 K) and exhibits a strong field dependence similar to the behavior of the Y${\mathrm{Ba}}_{2}$${\mathrm{Cu}}_{3}$${\mathrm{O}}_{7}$ superconductor.