Abstract

We present a full characterization of the anhydrous layered material K₂SrTa₂O₇ related to Ruddesden–Popper type phases. The unit cell, determined from powder X-ray diffraction, is tetragonal with a = 3.9858(1) Å and c = 21.785(1) Å (space group I4/mmm, Z = 2). The layered structure allows spontaneous water intercalation when the product is kept in air at ambient temperature. During hydration, a reversible structural transformation from an I to a P Bravais lattice is observed. By using K⁺/H⁺ ion exchange, in dilute HNO₃ or in acetic acid, we obtained the protonated phase H₂SrTa₂O₇·xH₂O which is compared to the one synthesized from Li₂SrTa₂O₇ previously reported by us. For both compounds, the hydration–dehydration behavior, studied by DTA/TGA and X-ray thermodiffractometry is discussed. In addition, we carried out an electron microscopy study of anhydrous K₂SrTa₂O₇ by selected area electron diffraction (SAED).