Exploring the Corundum Structure as a Host for Colored Compounds – Synthesis, Structures, and Optical Studies of (MM′)₃TeO₆ (M = Mg, Mn, Co, Ni, Zn; M′ = Mg, Mn, Co, Ni, Cu)

Abstract

We describe the syntheses, crystal structures, and optical absorption studies of the transition-metal-substituted corundum-related oxides (MM′) 3 TeO 6 (M = Mg, Mn, Co, Ni, Zn; M′ = Mg, Mn, Co, Ni, Cu). The oxides are readily synthesized by the solid-state reactions of stoichiometric mixtures of the constituent binaries at 750-860°C. The Rietveld refinements of the crystal structures from the powder X-ray diffraction (XRD) data show that the Mg/Mn/Ni/Co/ZnO 6 octahedra are distorted. We have interpreted the unique colors and the optical absorption spectra of these materials in terms of the distorted coordi- [a]

Crystal Chemistry, Optical Spectroscopy and Crystal Field Calculations of Co3TeO6 and Solid Solutions Co3–xZnxTeO6

“…as observed for the fully occupied CoO 4 tetrahedra in Ca 3 Co(SeO 3 ) 4 , and often also easily exceed CF absorption intensities of Co 2+ systems in sixfold oxygen coordination (apart from proportionally reduced intensities, the spectra of Co 0.01 Zn 2.99 TeO 6 comply with those of Co 0.05 Zn 2.95 TeO 6 and are not included in Figure ). Such high absorption coefficients are promising for the use of Co 3–x Zn x TeO 6 compounds as pigment materials, as recently also outlined, where DRIFT spectra (Vis range only) and powder photographs of the phases with x = 0, 1, 2 and 3 were presented (Figs. S26 and S27 in).…”

“…Such high absorption coefficients are promising for the use of Co 3–x Zn x TeO 6 compounds as pigment materials, as recently also outlined, where DRIFT spectra (Vis range only) and powder photographs of the phases with x = 0, 1, 2 and 3 were presented (Figs. S26 and S27 in). A comparison with our present DRIFT spectra (Figure ) with similar x values shows a reasonable agreement (albeit with a generally much lower Kubelka Munk scale and a tendency to compressed intensities towards higher energies in), whereas the powder photographs look surprisingly different from ours (Figure ; the closest visual match is found for their x Zn = 1 with our x Zn = 2.25 powder).…”

“…S26 and S27 in). A comparison with our present DRIFT spectra (Figure ) with similar x values shows a reasonable agreement (albeit with a generally much lower Kubelka Munk scale and a tendency to compressed intensities towards higher energies in), whereas the powder photographs look surprisingly different from ours (Figure ; the closest visual match is found for their x Zn = 1 with our x Zn = 2.25 powder).…”

“…It was pointed out in the Introduction section that during preparation of the present manuscript, DRIFT spectra of Co 3– x Zn x TeO 6 solid solutions have also been published elsewhere, emphasizing on the possible use as promising inorganic pigments. In the present article we focussed above on the structure–property relationships based on a detailed crystal field analysis.…”

“…Note that during preparation of the present manuscript, Rietveld refinements of Zn 2 CoTeO 6 and ZnCo 2 TeO 6 as well as DRIFT spectra of these solid solutions and of the end members have been published elsewhere, focussing on the possible use as inorganic pigments. Indeed, Co 3– x Zn x TeO 6 is a promising pigment material, but in the present article we will concentrate on the detailed crystal field analysis of Co 3– x Zn x TeO 6 phases and the relationships with structural and crystal chemical properties from more accurate single crystal data and over the complete range with x = 0–3.…”