Long Range Ordering of Interstitial Oxygen in Vanadium near V 4 O

Abstract

The crystal structure of interstitial solid solutions of vanadium with 14–23 at % oxygen has been determined by X-ray and electron diffraction. It is shown that the oxygen atoms occupy regularly the octahedral interstitial sites, forming a body-centered tetragonal superlattice of which the stoichiometry is approximately V 16 O 3 . The unit cell contains a 4×4×2 array of b.c.t. metal subcells with the axial ratio larger than unity. Both the cell dimensions of superlattice and sublattice increase of oxygen concentration. The superstructure is formed 400°C and transforms to another b.c.t. structure with preferential occupation of oxygen atoms like the Fe-C martensite above that temperature.