New mixed aluminium–chromium diarsenate

Abstract

Potassium chromium aluminium diarsenate, KCr1/4Al3/4As2O7, was prepared by solid-state reaction. The structure consists of (Cr1/4/Al3/4)O6octahedra and As2O7diarsenate groups sharing corners to build up a three-dimensional anionic framework. The potassium cations are located in wide channels running along thec-axis direction. The crystal structure is isostructural with the triclinicAIMIIIX2O7(AI= alkali metal;MIII= Al, Cr, Fe;X= As, P) compounds. However, theMIIIoctahedrally coordinated site is 25% partially occupied by chromium and 75% by aluminium.