Session: Chemistry of Materials:

Alkaline earth transition metal tetrasilicates exist in ABSi₄O₁₀ analog in the literature (A= Ca, Sr, Ba and B= Cr, Fe, Cu) where these materials show unique properties in their individual crystal structures. Though research has been carried out on ACrSi₄O₁₀, BaFeSi₄O₁₀, and ACuSi₄O₁₀systems over past decades, the chemistry of mixed transition metal centers in B-site of ABSi₄O₁₀ crystal structure remains largely unknown. Thus this study describes, for the first time, the preparation of mixed tetrasilicates containing Fe(II)/Cr(II), Fe(II)/Mn(II), and Cr(II)/Mn(II) in the known BaBSi₄O₁₀ system. We synthesize both Ba(Fe,Cr)Si₄O₁₀ and Ba(Fe,Mn)Si₄O₁₀ through a high temperature solid state route whereas Ba(Cr,Mn)Si₄O₁₀ forms via a alkali borate flux-based route. Interestingly, both the direct reactions of metal silicate, metal oxide, and elemental precursors and the reactions of pre-formed BaCrSi₄O₁₀ or BaFeSi₄O₁₀ with corresponding metal oxides provide access to all of the above-mentioned mixed tetrasilicates. Through the direct precursor reaction Ba(Fe,Cr)Si₄O₁₀ product forms with ~40% incorporation of Fe(II) into the BaCrSi₄O₁₀crystal structure; however, pre-formed tetrasilicate reactions increase the Fe(II) content up to ~60% while demonstrating the first ion exchange in tetrasilicates at high reaction temperature. We further find the range of iron incorporation in Ba(Fe,Cr)Si₄O₁₀analogs through the direct precursor reaction to be between ~20% and 40% Fe(II) with 40% being the maximum achievable iron incorporation under the designated conditions. Moreover, Ba(Fe,Mn)Si₄O₁₀ and Ba(Cr,Mn)Si₄O₁₀ reactions confirm ~20% incorporation of Mn(II) in both BaFeSi₄O₁₀ and BaCrSi₄O₁₀ systems via direct precursor reaction, which opens door to substitute other M(II) ions through templated growth mechanism. Crystals of mixed transition metal tetrasilicates were chemically exfoliated to yield multilayer thickness nanosheets with micron-sized lateral dimensions.

Harshani Niroshika Rathnaweera

Ph.D. Candidate, University of Georgia

Appearances