STRUCTURAL AND ELECTRIC PROPERTIES OF THE 2201-PHASE IN THE SYSTEM BI/PB-SR-CU-O

The effect of lead substitution on the structure, the oxygen content and the electrical properties of the 2201 system is studied. The "ideal" 2201 phase is absent for the ideal stoichiometry Bi2-xPbxSr2CuO6+z. However, a substitution of lead for strontium (system Bi2Sr2-xPbxCuO6+z) as well as a combined substitution of lead and bismuth for strontium (Bi2Sr2-x-yPbxBiyCuO6+z or lead for strontium and bismuth (B2-wSr2-xPbw+xCuO6+z) results in the formation of the 2201 phase. With increasing lead content the tetragonal subcell becomes orthorhombic and the specific resistivity increases. For a minimal lead content of x = 0.25 no transition to superconductivity was observed; however, in the semiconducting regime the temperature dependence of the specific resistivity is complex. Any attempt to prepare calcium containing 2201 phases results in the formation of a phase mixture between 2201 and 2212. © 1990.