The crystal structures of the high and low temperature forms of rhombohedral Cr-doped V 2O 3

Abstract

X-ray diffraction studies of single crystals of (Cr 0.01V 0.99) 2O 3 have shown that the transition from the low to high temperature rhombohedral forms of this material proceeds without changing the orientation of the unit cell axes. The structures of both the high and low temperature forms have been determined at 23°C using single crystal x-ray diffraction techniques. Both forms are isomorphous with V 2O 3, but upon heating the M-M distance across the shared octahedral face increases from 2.700(1) A to 2.747(1) A while the M-M distance across the shared edge increases from 2.884(1) A to 2.917(1) A. The M-O distances increase by a maximum of 0.011A. The low temperature form of (Cr 0.01V 0.99) 2O 3 is isostructural with V 2O 3 while the high temperature form is isostructural with (Cr 0.038V 0.962) 2O 3.