Neutron diffraction study of rubidium tungstate with a defect cubic pyrochlore-type structure: Rb1.10W1.66O5.53

Abstract

A neutron powder diffraction study of rubidium tungstate with a defect cubic pyrochlore-type structure has confirmed, and allowed the specification of, the structure previously established from X-ray powder diffraction. This structure corresponds to the formula Rb_1.10 W_1.66 O_5.53 with 17 and 8% of tungsten and oxygen vacancies in the W–O framework. Rb⁺ cations are localized in two positions; the best model was obtained with the formula Rb_0.17(96g)Rb_0.93(8b)W_1.66(16c)O_5.53(48f) in the Fdem space group. Rb(96g) has an eight oxygen coordination polyhedron and Rb(8b) has an 18 oxygen coordination polyhedron with Rb–O bond lengths between 2.839 and 3.966 Å.