Synthesis and structure of a double-layered perovskite and its hydrate, K2SrTa2O7·mH2O (m = 0, 2)

Studies on the known compound, K2SrTa2O7, and its hydrate are reported. A method for preparing single-phase samples is presented. Rietveld structural refinement of X-ray powder diffraction data verify that K2SrTa2O7 is an n = 2 member of the Ruddlesden–Popper series; K2SrTa2O7 was refined on the body-centered tetragonal space group I4/mmm with a = 3.9768(1) Å and c = 21.7062(6) Å. This compound readily hydrates in air to form K2SrTa2O7·2H2O. Structural analysis on a primitive tetragonal cell (P4/mmm), where a = 3.9599(1) Å and c = 12.7568(3) Å, shows that on intercalation of water the staggered perovskite layers of K2SrTa2O7 shift to an eclipsed configuration.