Sr–fresnoite determined from synchrotron X-ray powder diffraction data

The fresnoite-type compound Sr(2)TiO(Si(2)O(7)), distrontium oxidotitanium disilicate, has been prepared by high-temperature solid-state synthesis. The results of a Rietveld refinement study, based on high-resolution synchrotron X-ray powder diffraction data, show that the title compound crystallizes in the space group P4bm and adopts the structure of other fresnoite-type mineral samples with general formula A(2)TiO(Si(2)O(7)) (A = alkaline earth metal cation). The structure consists of titanosilicate layers composed of corner-sharing SiO(4) tetra­hedra (forming Si(2)O(7) disilicate units) and TiO(5) square-based pyramids. These layers extend parallel to the ab plane and are stacked along the c axis. Layers of distorted SrO(6) octa­hedra lie between the titanosilicate layers. The Sr(2+) ion, the SiO(4) tetra­hedron and the bridging O atom of the disilicate unit are located on mirror planes whereas the TiO(5) square-based pyramid is located on a fourfold rotation axis.