Aluminum substitution in Ba2YCu3O7

Abstract

We have investigated the effect of aluminum incorporation on the structure and superconducting transition temperature of single crystals of high-$T_c$ cuprate perovskite superconductors. The use of alumina crucibles for crystal growth results in incorporation of aluminum to varying extents in crystals of composition ${\mathrm{Ba}}_2\mathrm{Y}{\mathrm{Cu}}_{3-x}{\mathrm{Al}}_x{\mathrm{O}}_7$, $x=0-0.22\mathrm{}$. We have performed x-ray studies on several crystals to determine structural effects of Al incorporation. We find that aluminum substitutes only for copper atoms in the chains. Superconducting transition temperatures $T_c$ determined by dc diamagnetic susceptibility measurements change only slightly, to ∼80 K for $x=0.1\mathrm{}$, then drop sharply with higher aluminum concentrations. Results are discussed in relation to the importance of the Cu-O chains and oxygen stoichiometry to superconductivity in ${\mathrm{Ba}}_2$Y${\mathrm{Cu}}_3$ ${\mathrm{O}}_7$.