Ga置換によるフッ素雲母の赤外線吸収スペクトル及び格子定数の変化

抄録

The series of Ga-substituted fluorine micas, KMg_2+xLi_1-x(Ga_xSi_4-x-yGe_yO₁₀)F₂ and KMg_2+xLi_1-x(Ga_xGe_4-x-ySi_yO₁₀)F₂; x=0.0-1.0, y=0, 1, 2, 3, were synthesized and the changes in infrared spectra and lattice constants with Ga-substitution were studied. The larger flakes of mica crystals were obtained with increasing Ga- and Ge-contents. The infrared spectra of the synthesized micas varied sensitively with mica composition. An absorption band, which appeared in the range 740-705cm^-1 with increasing Ga-content, is attributable to Ga-O vibration. Continuous changes of lattice constants with increasing Ga-contents proved that there were complete series of solid solutions between the end member micas. Lattice constants a and b increased linearly or almost linearly with increasing Ga-content in all series. However, c⋅sinβ (basal spacing) decreased or remained almost unchanged in the case of Ga-for-Ge substitution, while it increased linearly in the case of Ga-for-Si substitution. These complicated changes of cell dimensions were shown clearly by the plots of c⋅sinβ vs. b-dimension and explained in terms of the tetrahedral rotation angle α, the octahedral flattening angle ψ, and the change of interlayer conformation, where α and ψ show the degree of structural deformation in mica structure. It is also indicated that the degree of structural deformation increased with increasing Ga and Ge contents.