h4atedds Rosearch EadMin, Vol. 30, No. 8. pp. 925431.1995 Cqy@J1tQ1995Elswi~SoimosLb.l RiokdintheusA.Aurighlam8aved 0025~5408/95 $9.50 + .OO CONTRIBUTION TO THE STRUCTURAL CHARACTERIZATION OF A SODIUM YTTRIUM TITANATE LAYERED PEROVSKITE AND ITS PROTONATED FORMS Mireille RICHARD, Graziella GOGLIO and Luc BROHAN Institut des Mat6riaux de Names, Iaboratoire de Chimie des Solides UMR CNRS No 110 - Universit6 de Names 2, rue de la Houssin&e, 44072 NANTBS CBDEX 03, France (Received April 30, 1995; Communicated by P. Hagenmuller) ABSTRACT : The layered perovskite structures of NaYTiO, and homologous acid exchange form were investigated via powder X-ray diffraction and high resolution transmission electron microscopy. The NaYTiO? layered structure differs from the previous investigation of Blasse et al., by the mcorporation of pemvskite-like 2 octahedra thick lamellae instead of 1 octahedron thick lamellae and by a stacking of slabs which is primitive instead of I-centered with an (a+b)/2 gliding. The exchange of Na’ cations was performed in an acid medium. This experiment suggests that half of the Y3+ions occupy the perovskite lie cavities whereas the Na’ cations are localized in the interlayer space. Consequently, this structure is probably closer to TIBa,CaCulO, family compounds than to A,,rB,03,,, Ruddlesden-Popper type structure with n= 1. MATERIALS INDEX : titanate layered perovskite, acid-exchange, electron microscopy. . htroductlu Due to their potential application in catalysis for instance, there is a great interest in structures derived from perovskite. We are particularly interested in compounds known as Ruddlesden- Popper structures, An+ 1 B,Ojn+ l(1). Their connection with the perovskite lies in the structure of the layers. In An+IBn03,,+I, n perovskite slabs constitute each layer which is stacked with a 112 gliding along two of the cubic crystallographic directions of the 3D perovskite, namely a (a+b)/2 gliding. We reported elsewhere the structural investigations concerning the n = 3 term, A&n2Ti3OIo where A is an alkali or a proton and Ln is a rare earth or yttrium (2,3). In an attempt to synthesize other terms of this family, a compound with layers each containing two perovskite slabs was obtained. In this paper, the structural characterization of NaYTiOq and its protonated forms, using powder XRD and high resolution electron microscopy, is reported and discussed. 925