Structural changes in the solid solution (Ti1−xVx)2O3 as x varies from zero to one

The crystal structures of (Ti1−xVx)2O3, x = 0.005, 0.01, 0.02, 0.04, 0.07, 0.30, 0.50, 0.70, and 0.90, have been determined from X-ray diffraction data collected from single crystals. The compounds are rhombohedral, space group R3c, and are isomorphous with α-alumina. The hexagonal cell dimensions range from a = 5.1549(6)Å, c = 13.627(2)Å, for (Ti0.995V0.005)2O3 to a = 4.9813(2)Å, c = 13.996 (1)Å for (Ti0.10V0.90)2O3. The most pronounced effects of V3+ substitution occur in the 0 to 7 at% V range and can be described as an increase in the metal-metal distance along the c axis from 2.578(2) Å in pure Ti2O3 to 2.652(1) Å in (Ti0.93V0.07)2O3 coupled with reorganization of the structure in order to maintain constant metal-oxygen distances. These structural changes have been related to both the change from semiconducting to metallic behavior and the disappearance of the 150–350°C resistivity drop which occur with increasing vanadium content in (Ti1−xVx)2O3 as x increases from 0.0 to about 0.07. They are consistent with the band theory proposed by others for this system. Indications of unusual structural behavior in the 90–100 at% V range are also noted.