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 ACuSi4O10 systems 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 BaCrSi4O10 crystal 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)Si4O10 analogs 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.

Preparation and nanostructuring of Fe(II)/Mn(II), Cr(II)/Mn(II) and Fe(II)/Cr(II) containing tetrasilicates

ACS Spring Meeting 2021

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