Composition and superconductivity in single layer Bi-2201 phases


  • Dedicated to E. Bayer on the occasion of his 65th birthday.


Several materials with nominal 2201 composition were prepared from various systems Bi2+xSr2-xCuO6+z, Bi2Sr2-xCuO6+z, Bi2-xPbxSr2O6+z, Bi2.1-xPbxCuO6+z,Bi2Sr2-yLayCuO6+z, Bi1.9Pb0.1Sr2-yLayCuO6+z, Bi2-xPbxSr1.6La0.4CuO6+z and Bi2.1-xPbxSr1.5La1.4CuO6+z in different gas atmospheres. According to the structural investigations the 2201 phase shows solid solution behaviour. However, irrespectively of the method of preparation the appearance of superconductivity is confined to multiphase material. Furthermore, the superconducting volume fraction is uniformly as low as ≲ 3%. The observed presence of trace superconductivity is easily explainable by small admixtures of superconducting foreign phases and in disagreement with the assumption of intrinsic superconducting properties of the Bi based 2201 phase.