Malayaite ceramic pigments: A combined optical spectroscopy and neutron/X-ray diffraction study

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• 作者：Giuseppe Cruciani ; Michele Dondi ; Matteo Ardit ; Teodora Stoyanova Lyubenova ; Juan B. Carda ; Francesco Matteucci ; Anna L. Costa
• 关键词：A. Ceramics ; C. X-ray diffraction ; D. Crystal structure ; D. Optical properties
• 刊名：Materials Research Bulletin
• 出版年：2009
• 出版时间：5 August 2009
• 年：2009
• 卷：44
• 期：8
• 页码：1778-1785
• 全文大小：444 K

文摘

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.