Malayaite ceramic pigments: A combined optical spectroscopy and neutron/X-ray diffraction study |
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Authors: | Giuseppe Cruciani Matteo Ardit Teodora Stoyanova Lyubenova Francesco Matteucci |
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Affiliation: | a Department of Earth Sciences, University of Ferrara, Via Saragat 1, 44100 Ferrara, Italy b ISTEC-CNR, Institute of Science and Technology for Ceramics, Via Granarolo 64, 48018 Faenza, Italy c Department of Inorganic and Organic Chemistry, University Jaime I, Campus Riu Sec, 12071 Castellón, Spain |
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Abstract: | Ceramic pigments based on the Cr-doped malayaite structure were synthesized by solid state reaction and characterized by optical spectroscopy and combined X-ray and neutron powder diffraction in order to elucidate the still unclear chromium substitution mechanisms. The results show that coloration is actually due to simultaneous occurrence of Cr4+ and Cr3+ ions in the crystal lattice. Spectroscopy data confirm that Cr4+ is replacing Sn4+ in the octahedral site and, in minor amount, Si4+ in the tetrahedral site. In addition, neutron powder diffraction data suggest that Cr3+ substitution for octahedral Sn4+ is charge balanced by the formation of oxygen vacancies with no preference over the different oxygen sites. Upon incorporation of Cr ion, the SnO6 octahedra exhibit an off-centre displacement of central cation which in turn induces a rearrangement of both the octahedral and tetrahedral coordination shells. |
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Keywords: | A. Ceramics C. X-ray diffraction D. Crystal structure D. Optical properties |
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