(Ba,K)3Bi2O7: A layered bismuth oxide

Abstract

The synthesis and crystal structure of a new perovskite-based bismuth oxide are reported. The phase, of composition ${\mathrm{Ba}}_{1.7}$ ${\mathrm{K}}_{1.3}$ ${\mathrm{Bi}}_2$ ${\mathrm{O}}_7$, is the n=2 member of the Ruddlesden-Popper series ${\mathit{A}}_{\mathit{n}+1\mathrm{}}$ ${\mathit{B}}_{\mathit{n}}$ ${\mathrm{O}}_{3\mathit{n}+1\mathrm{}}$. It has tetragonal symmetry, space group I4/mmm, with unit-cell dimensions a=4.2477(6) Å, and c=21.885(3)Å. The phase is synthesized for the alkali metals K and Rb from KOH (RbOH)+Ba(OH${)}_2$⋅${\mathrm{H}}_2$O melts. The stoichiometry is apparently not easily varied. The phase is not superconducting down to 2 kelvin.