Crystal structure, optical properties and colouring performance of karrooite MgTi{sub 2}O{sub 5} ceramic pigments
- ISTEC-CNR, Institute of Science and Technology for Ceramics, Via Granarolo 64, 48018 Faenza (Italy)
- Department of Earth Sciences, University of Ferrara, Via Saragat 1, 44100 Ferrara (Italy)
- Department of Earth and Geo-Environmental Sciences, University of Bologna, Piazza di Porta San Donato 1, 40126 Bologna (Italy)
Karrooite, MgTi{sub 2}O{sub 5}, is a promising ceramic pigment due to its high refractoriness and refractive indices, as well as its ability to host transition metal ions in two crystallographically distinct octahedral sites. The colouring performance was investigated combining X-ray powder diffraction with UV-vis-NIR spectroscopy on karrooite doped with V, Cr, Mn, Fe, Co or Ni (M) according to the formula Mg{sub 1-x}Ti{sub 2-x}M{sub 2x}O{sub 5}, with x=0.02 and 0.05. Transition metals solubility in the karrooite lattice is not complete and a second phase is always present (geikielite or rutile). Structural data proved that incorporation of different chromophore ions into the karrooite structure affects unit cell parameters, bond length distances and angles, site occupancies and therefore cation order-disorder. Optical spectra exhibit broad absorbance bands of Co(II), Cr(IV), Fe(III), Mn(II), Mn(III), Ni(II), V(IV) with distinct contributions by cations in the M{sub 1} and M{sub 2} sites. Karrooite pigments have colours ranging from orange to brown-tan (Cr, Fe, Mn, V) to green (Co) and yellow (Ni) that are stable in low-temperature (<1050 deg. C) ceramic glazes and glassy coatings. - Graphical abstract: Karrooite is a promising ceramic pigment for high refractoriness and refractive indices. Incorporation of V(IV), Cr(IV), Mn(II)+Mn(III), Fe(III), Co(II) or Ni(II) in two crystallographically distinct octahedral sites affects unit cell parameters, bond length distances and cation order-disorder, leading also to distinct optical bands from the two different sites, so reducing colour purity.
- OSTI ID:
- 21043744
- Journal Information:
- Journal of Solid State Chemistry, Vol. 180, Issue 11; Other Information: DOI: 10.1016/j.jssc.2007.08.029; PII: S0022-4596(07)00368-4; Copyright (c) 2007 Elsevier Science B.V., Amsterdam, The Netherlands, All rights reserved; Country of input: International Atomic Energy Agency (IAEA); ISSN 0022-4596
- Country of Publication:
- United States
- Language:
- English
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