Site confirmation of Fe³⁺ in a synthetic ferrian aluminian diopside with an application of X-ray anomalous dispersion

抄録

Crystals of ferrian aluminian diopside were synthesized and the structures were investigated by means of a single-crystal X-ray diffraction method in detail. EPMA gave the chemical formula of Ca_1.00(Mg_0.55Fe³⁺_0.37Al_0.08)(Si_1.55Al_0.45)O₆ for the crystals as an average. Structure refinement indicated that about 9 % of Fe³⁺ ions are at T sites, giving the formula of Ca_1.00(Mg_0.55Fe³⁺_0.34Al_0.11)(Si_1.55Al_0.42Fe³⁺_0.03)O₆. Existence of Fe³⁺ at T sites was, however, not confirmed on a difference Fourier map synthesized by making use of anomalous dispersion effect at the Fe K absorption edge. The bond distances are reasonable for a ferrian aluminian diopside with a chemical composition found for the present crystals.