Phase transitions in the system Ba-K-Pb-Bi-O

Abstract

Ba(Pb, Bi)O₃ is known to be a superconductor for appropriate concentration of bismuth. On the other hand, all known high-T_c oxide superconductors show two-dimensional sheet structures. In an hypothetical Ba₂(Pb,Bi)O₄ system, both ingredients would be combined. The latter system is found to exist, isostructural to La₂CuO₄, but being an insulator. This paper shows how to induce an insulator-metal phase transition in this series by potassium doping. The electronic carrier concentration is checked by screening of phonons in infrared reflectivity spectra.