The dehydration Q2 of SrTeO3(H2O) - a topotactic reaction for preparation of the new metastable strontium oxotellurate(IV) phase ε-SrTeO3

STÖGER, BERTHOLD; WEIL, MATTHIAS; BARAN, ENRIQUE J.; GONZÁLEZ BARÓ, ANA C.; MALO, SYLVIE; RUEFF, JEAN MICHEL; PETIT, SEBASTIEN; LEPETIT, MARIE BERNADETTE; RAVEAU, BERNARD; BARRIER, NICOLAS

DALTON TRANSACTIONS

ROYAL SOC CHEMISTRY

Año: 2011 vol. 40 p. 5538 - 5548

1477-9226

Microcrystalline single-phase strontium oxotellurate(IV) monohydrate, SrTeO3(H2O), was obtained bymicrowave-assisted hydrothermal synthesis under alkaline conditions at 180 ºC for 30 min. Atemperature of 220 ºC and longer reaction times led to single crystal growth of this material. Thecrystal structure of SrTeO3(H2O) was determined from single crystal X-ray diffraction data: P21/c,Z = 4, a = 7.7669(5), b = 7.1739(4), c = 8.3311(5)A , b = 107.210(1)º, V = 443.42(5)A 3, 1403 structurefactors, 63 parameters, R[F2>2s(F2)] = 0.0208, wR(F2 all) = 0.0516, S = 1.031. SrTeO3(H2O) is isotypicwith the homologous BaTeO3(H2O) and is characterised by a layered assembly parallel to (100) ofedge-sharing [SrO6(H2O)] polyhedra capped on each side of the layer by trigonal-prismatic [TeO3] units.The cohesion of the structure is accomplished by moderate O–H---O hydrogen bonding interactionsbetween donor water molecules and acceptor O atoms of adjacent layers. In a topochemical reaction,SrTeO3(H2O) condensates above 150 ºC to the metastable phase e-SrTeO3 and transforms upon furtherheating to d-SrTeO3. The crystal structure of e-SrTeO3, the fifth known polymorph of this composition,was determined from combined electron microscopy and laboratory X-ray powder diffraction studies:P21/c, Z = 4, a = 6.7759(1), b = 7.2188(1), c = 8.6773(2)A , b = 126.4980(7)º, V = 341.20(18)A 3, RFobs =0.0166, RBobs = 0.0318, Rwp = 0.0733, Goof = 1.38. The structure of e-SrTeO3 shows the same basicset-up as SrTeO3(H2O), but the layered arrangement of the hydrous phase transforms into a frameworkstructure after elimination of water. The structural studies of SrTeO3(H2O) and e-SrTeO3 arecomplemented by thermal analysis and vibrational spectroscopic measurements.