Synthesis and structural characterization of novel tin and titanium potassium silicates K4M2Si6O18

The synthesis of a new potassium titanosilicate, K₄Ti₂Si₆O₁₈ (Ti-AV-11), possessing the crystal structure of potassium stannosilicate AV-11, has been reported. The unit cell of this material is trigonal, space group R3 (no. 146), Z=3, a=10.012, c=14.8413 Å, γ=120°, V=1289 Å³. The structure of AV-11 is built up of MO₆ (M=Sn, Ti) octahedra and SiO₄ tetrahedra by sharing corners. The SiO₄ tetrahedra form helix chains, periodically repeating every six tetrahedra. These chains extend along the 001] direction and are linked by isolated MO₆ octahedra, thus producing a mixed octahedral-tetrahedral oxide framework. AV-11 materials have been further characterized by bulk chemical analysis, powder X-ray diffraction (XRD), scanning electron microscopy (SEM), ²⁹Si and ¹¹⁹Sn magic-angle spinning (MAS) NMR spectroscopy.