New mixed aluminium–chromium diarsenate

Abstract

The title compound structure consists of (Cr _1/4/Al _3/4)O ₆ octa­hedra and As ₂O ₇ diarsenate groups sharing corners to build up a three-dimensional anionic framework. The potassium cations are located in wide channels running along the c-axis direction.

Abstract

Potassium chromium aluminium diarsenate, KCr _1/4Al _3/4As ₂O ₇, was prepared by solid-state reaction. The structure consists of (Cr _1/4/Al _3/4)O ₆ octa­hedra and As ₂O ₇ diarsenate groups sharing corners to build up a three-dimensional anionic framework. The potassium cations are located in wide channels running along the c-axis direction. The crystal structure is isostructural with the triclinic A ^I M ^III X ₂O ₇ ( A ^I = alkali metal; M ^III = Al, Cr, Fe; X = As, P) compounds. However, the M ^III octa­hedrally coordinated site is 25% partially occupied by chromium and 75% by aluminium.