Charge homogeneity in synthetic fluorohectorite

Due to phase separation in the silicate melt, the synthesis of fluorosmectites ([Na-0.5](inter)[Mg2.5Li0.5](oct)[Si-4](O10F2)-O-tet) from the melt without mechanical mixing yields an inhomogeneous material. Because of the solid solution capability of the 2:1 layer silicate structure, the nonuniformity in chemical and mineral composition inevitably will lead to fluorosmectites that adopt a range of charge densities. This will be detrimental to many possible applications due to the large influence of layer charge on the properties of clay minerals. The problem can be circumvented by rotating the crucible during synthesis in a horizontal mounting, which will continuously force mixing of the melt mechanically. The product obtained is homogeneous at all length scales as judged by chemical analysis and its uniform intracrystalline reactivity. Noteworthy is its tendency to form regularly interstratified intercalates of monolayers and bilayers upon alkylammonium exchange and of rectorite type phases upon partial K+ exchange. We expect that the two dissimilar types of galleries, which are stacked in a regularly alternating pattern, can be selectively addressed-leading to interesting intercalation materials.