Assembly of Metal-Anion Arrays within Dion-Jacobson-Type Perovskite Hosts
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Assembly of Metal-Anion Arrays within Dion-Jacobson-Type Perovskite Hosts Thomas A. Kodenkandath,† Marilena L. Viciu, Xiao Zhang, Jessica A. Sims, Erin W. Gilbert, François-Xavier Augrain, Jean-Noël Chotard, Gabriel A. Caruntu, Leonard Spinu, Weilie L. Zhou, and John B. Wiley* Department of Chemistry and the Advanced Materials Research Institute, University of New Orleans, New Orleans, LA 70148-2820 [email protected] ABSTRACT The construction of metal-anion arrays within Dion-Jacobson-type (DJ) perovskites was studied. A variety of hosts readily react with CuCl2 to produce compounds of the form (CuCl)[A’n-1(M,M’)nO3n+1] (A’ = alkaline earth, rare earth or Bi; M/M’ = Nb, Ta, and/orTi; n = 2, 3). In contrast, CuBr2 only reacts with some of these hosts; this difference relative to the chloride may simply be a size effect. The formation of metal-anion arrays with other transition metals has also been examined. (FeCl)LaNb2O7 can be readily prepared from FeCl2, while reactions with FeBr2 and NiCl2 under similar reaction conditions result in compounds of the form M0.5LaNb2O7 (M = Fe, Ni). The reductive intercalation of lithium and sodium into (CuCl)LaNb2O7 was also examined and was found to produce new compounds that have a large layer expansion.
INTRODUCTION Low-temperature (& VWUDWHJLHVEDVHGRQWRSRWDFWLFPHWKRGVDUHFXUUHQWO\EHLQJ explored for the directed synthesis of new materials. Exploitation of methods involving ion exchange and/or (de)intercalation offers an important approach to the control of valence and structure in receptive hosts. Recent efforts, in perovskite-related compounds for example, have resulted in the preparation of new mixed-valence titanates, niobates and tantalates [1-4], alternating layered 3-D perovskites [5], and mixed-metal compounds [6,7]. Similarly, our group has been examining the construction of metal-anion arrays within Dion-Jacobson-type perovskite hosts [8,9]. We recently reported the synthesis of (CuX)LaNb2O7 (X = Cl, Br). Herein we describe the extension of this chemistry to other host systems and other transition-metal halides as well as the behavior of (CuCl)LaNb2O7 with respect to reductive intercalation.
EXPERIMENTAL Synthesis. Compounds belonging to the Dion-Jacobson (DJ) series of layered perovskites, A[A’n-1(M,M’)nO3n+1] (A = alkali metal, H, NH4, A’ = alkaline earth, rare earth or Bi, M/M’ = Nb, Ta, Ti, n = 2, 3) were synthesized by standard high-temperature solid-state or low-temperature ion exchange reaction methods as described in the literature [10-15]. Starting mixtures for compounds where A = K, Rb were made with the stoichiometric amounts of the appropriate oxides and a 20 - 25% molar excess of A2CO3 (to compensate for the loss of the oxide due to † *
Current address American Superconductor, Westborough, MA 01581 To whom correspondence should be addressed
GG8.5.1
volatilization). Reagents were ground together and heated in alumina reaction vessels at 850 900°C for 12 h and then 1050 - 1100°C for 24 - 48 h with one intermittent grinding. The products were w
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