Emergence of superconductivity in a bi-sr-cu-o system

Abstract

Solid solutions of ${\left({\mathrm{Bi}}_{2-x}{\mathrm{Sr}}_x\right)}_2\mathrm{Cu}{\mathrm{O}}_6$ ($0.8\le x\le 1.5$) have been synthesized. A metal-insulator transition is observed as the Sr composition is reduced to 0.9. The emergence of superconductivity depends critically on the minimum Sr content. Only when $x\ge 0.95$, does the superconductivity occur. The behavior is different from that observed in the ${\mathrm{La}}_{2-x}{\mathrm{Sr}}_x\mathrm{Cu}{\mathrm{O}}_4$ system where doping ${\mathrm{La}}_2$Cu${\mathrm{O}}_4$ by Sr brings the system into a metallic and superconducting phase, with gradually increasing $T_c$.