Crystal Structure of Bi 2O 4 with β-Sb 2O 4-Type Structure

Abstract

A new mixed valent bismuth oxide, Bi 3+Bi 5+O 4, was prepared by a low temperature hydrothermal reaction using a hydrated sodium bismuth oxide, NaBiO 3 · nH 2O, as a starting material. This oxide is isostructural with β-Sb 2O 4 and the lattice parameters are a = 12.3668(2), b = 5.1180(1), c = 5.5670(1) Å and β = 107.838(1)° in the monoclinic system. The crystal structure was refined using high resolution neutron powder diffraction data resulting in R WP = 7.76, R p = 6.01, R E = 5.98, and R I = 2.02%. In this mixed valent bismuth oxide, Bi 3+ and Bi 5+ occupy distinct crystallographic sites, Bi 3+ being coordinated by eight oxygens and Bi 5+ being octahedrally coordinated by six oxygens. The structure can be related to the CaF 2-type structure. This mixed valent bismuth oxide decomposes to Bi 2O 3 via an intermediate phase with mixed valent states with weight loss caused by reduction of Bi 5+ to Bi 3+ at elevated temperatures.