Structure and Phase Transformations in the Titanosilicate, Sitinakite. The Importance of Water

Synchrotron X-ray diffraction and neutron diffraction have been used to investigate the phase changes that the titanosilicate mineral sitinakite undergoes when dehydrated. Refinements of the powder diffraction data of the material before and after heating to 573K indicate a phase change from space group P 4 2 / mcm to P 4 2 / mbc . Upon exposure to normal atmospheric conditions for an extended period the material transforms back to P 4 2 / mcm with a reduced lattice parameter. If the material is heated in a sealed capillary, it is possible to get the two phases coexisting. The coexistence of these two phases in sealed system suggests that it is only the loss of H 2 O that is driving the reversible phase transformation.