Novel mixed-framework silicates containing trivalent cations

The aim of the project was the synthesis and characterisation of new microporous and small-pore mixed- framework silicates containing octahedrally coordinated M 3+ cations. Such mixed-framework silicates were previously very poorly investigated in comparison to the well-studied, related classes of titanosilicates and zirconosilicates. A large number of previously unknown M 3+-bearing mixed-framework silicates were prepared using flux (1150C) and hydrothermal syntheses (230C) in the system M 1+-(M2+-) M 3+-Si-O(-H) (M = Na, K, Rb, Cs; M = Sr, Ba; M = Sc, V, Cr, Fe, In, Y, Yb). The crystal structures of the novel silicates were determined in detail, chemical compositions and spectroscopic properties were characterised, and potential technical applications were discussed. The synthesised silicates are expected, on the basis of their novel atomic arrangements, to have promising physico- chemical properties (e.g., with possible application as ion exchange materials, catalysts, luminescent materials and immobilisers for radioactive cations and heavy metal waste, etc.). The project`s results will also help to improve the further development of the flux-growth technique as applied to the preparation of microporous and other mixed-framework silicates.