Mn, Mg, and Zn ilmenite group titanates: A reconnaissance rietveld study

Ecandrewsite-geikielite (Zn_1/2Mg_1/2TiO₃), ecandrewsite-pyrophanite (Zn_1/2Mn_1/2TiO₃), pyrophanite-geikielite (Mg_1/2Mn_1/2TiO₃), and ecandrewsite-pyrophanite-geikielite (Zn_1/3Mn_1/3Mg_1/3TiO₃) titanates were synthesized at 900–1000°C at ambient pressure. All of the compounds adopt R— ilmenite-type structures. These structures were refined by the Rietveld method from X-ray powder diffraction data. Unit cell parameters and unit cell volumes decrease with decreasing average radii of the A²⁺ cation. All structures consist of distorted AO₆ and TiO₆ octahedra. In common with pyrophanite and ilmenite, the distortion of the AO₆ octahedra is less than that of the TiO₆ octahedra. Data are given for the volumes and distortion indexes of all coordination polyhedra.