Synthesis of New Multiple Layered Dion-Jacobson Perovskites
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Synthesis of New Multiple Layered Dion-Jacobson Perovskites Léa Gustin, Jérôme Lefebvre, Clare Davis-Wheeler, Amy K. Pressley and John B. Wiley* Department of Chemistry and Advanced Materials Research Institute, University of New Orleans, New Orleans, LA 70148 ABSTRACT New multiple layered perovskites with general formula RbLaNaxNb2+xO7+3x, x = 1 and 2, were synthesized via a ceramic method. While the triple layered compound could be obtained by simple direct reaction, the quadruple layered one was synthesized using a two-step solid state approach. The compounds were characterized by X-ray powder diffraction; the newly obtained compounds appear to be isostructural with the previously reported RbCa2Nb3O10 and RbCa2NaNb4O13 for RbLaNaNb3O10 and RbLaNa2Nb4O13, respectively. Preliminary results show that the new compounds can undergo ion exchange reactions involving alkali metals and transition metal chlorides. INTRODUCTION The Dion-Jacobson (DJ) series of layered perovskites have the general formula A[A´nB O 1 n 3n+1], where typically A = alkali metal, A´= rare earth or alkaline-earth, B = transition metal, and n = number of perovskite layers. The double- and triple-layered compounds, such as RbLaNb2O7 and RbCa2Nb3O10, respectively, are among the most studied [1,2]. The multilayered perovskites K[Ca2Nan-3NbnO3n+1] (3 ≤ n ≤ 7) are also known and can be obtained via the solidstate reaction between the layered perovskite KCa2Nb3O10 and the simple perovskite NaNbO3 [3]. This series of compounds exhibit a range of important properties including photocatalytic activity, ionic conductivity, and superconductivity [4-6]. Special interest in these phases also comes from their utility in topochemical reactions such as ion exchange and intercalation, leading the way to number of new metastable compounds not accessible by traditional ceramic methods [7]. In spite of the range of interesting properties, there are relatively few DJ compounds available for study. We have therefore been working to develop new DJ structures for use in topochemical reaction studies. Herein we report the one step synthesis of the new triple layered compound RbLaNaNb3O10. Also using the approach developed by Jacobson et al. [3], the quadruple layered RbLaNa2Nb4O13 was obtained by reacting RbLaNb2O7 and NaNbO3. Additionally, topotactic manipulations at low temperatures (< 500 °C) were attempted on the new products with ANO3 (A = alkali metals) and first row transition metals halides in order to expand the family of new layered perovskites. Details on the synthesis and characterization of this series of compounds are presented and their potential utility in further topochemical manipulations discussed.
EXPERIMENTAL Synthesis RbLaNaNb3O10 was prepared by ceramic method from Rb2CO3 (Rb2CO3 Alfa Aesar 99%), La2O3 (Alfa Aesar, 99.99%), Na2CO3 (Alfa Aesar, 99.997% anhydrous) and Nb2O5 (Alfa Aesar, 99.9985%). La2O3 and Nb2O5 were both heated to 1000°C for 24 h before reaction to remove any hydroxides or carbonates. Stoichiometric amounts of the oxides along with
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