Layered titanosilicates – A review and some results on the hydrothermal synthesis of bafertisite

Heterophyllosilicates are titanosilicate minerals based on layers which, via a periodic substitution of rows of Si-tetrahedra by rows of Ti-polyhedra, can be formally derived from the tetrahedral–octahedral–tetrahedral (TOT) layer of phyllosilicates. According to the periodicity of the substitution, three types of HOH layers (H to indicate the hetero substitution) are known: bafertisite-, astrophyllite- and nafertisite-type. Based on parallelism between the crystal structures of heterophyllosilicates and phyllosilicates, the paper aims to draw the attention of materials scientists on a possible use of bafertisite-type compounds to produce layered materials of technological interest. Some preliminary results on the hydrothermal synthesis of bafertisite are presented. By EDS electron-microprobe chemical analysis, optical and electron microscopy, and X-ray powder diffraction, a minor presence of bafertisite has been established in a mixture of synthesis products that include gillespite and fresnoite.