STRUCTURE DETERMINATION OF ALPHA-TIOSO4 FROM POWDER X-RAY-DIFFRACTION DATA

αTiOSO4 forms as a leach-resistant phase during the digestion of altered ilmenite concentrates in concentrated sulphuric acid. It contains about 7 wt% Fe2O3 and its composition can be expressed as Ti0.85Fe0.15O0.85(OH)0.15SO4. It has monoclinic symmetry, space ` C2 c, and unit cell parameters a = 5.1175(2), b = 13.7675(6), c = 9.5035(4)Å, β = 91.097(3)°. Its structure was determined using powder X-ray diffraction data and refined by the Rietveld method to Rwp = 0.059, RB = 0.022, goodness of fit = 1.56 for 706 reflections to 2θ = 140°, CuKα radiation. The structure comprises a 3-D framework of corner-linked Ti1O6 and Ti2O6 octahedra and SO4 tetrahedra, with six-sided channels running parallel to both [100] and [001]. Alternating corner-shared octahedra and tetrahedra form four-member rings which link together into ribbons via the constituent octahedra. Ribbons containing Ti1O6 and Ti2O6 octahedra lie along [001] and [100], respectively, and differ in the relative positions of the pairs of vertices forming the four-member rings. Structural relationships between αTiOSO4 and other phases containing corner-linked octahedra and tetrahedra are described. © 1992.