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Structure and thermal behavior of the new superprotonic conductor Cs_2(HSO_4)(H_2PO_4)

Chisholm, Calum R. I. and Haile, Sossina M. (1999) Structure and thermal behavior of the new superprotonic conductor Cs_2(HSO_4)(H_2PO_4). Acta crystallographica. Section B, Structural science, 55 (6). pp. 937-946. ISSN 0108-7681. doi:10.1107/S0108768199009921.

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Ongoing studies of the CsHSO_4-CsH_2PO_4 system, aimed at developing novel proton conducting solids, resulted in the new compound Cs_2(HSO_4)(H_2PO_4) (dicesium hydrogensulfate dihydrogenphosphate). Single-crystal X-ray diffraction (performed at room temperature) revealed Cs_2(HSO_4)(H_2PO_4) to crystallize in space group P2_1/n with lattice parameters a = 7.856 (8), b = 7.732 (7), c = 7.827 (7) Å, and β = 99.92 (4)°. The compound has a unit-cell volume of 468.3 (8) Å3 and two formula units per cell, giving a calculated density of 3.261 Mg m^(-3). Six non-H atoms and two H atoms were located in the asymmetric unit, with SO_4 and PO_4 groups randomly arranged on the single tetrahedral anion site. Refinement using all observed reflections yielded weighted residuals of 0.0890 and 0.0399 based on F(2) and F values, respectively. Anisotropic temperature factors were employed for all six non-H atoms and fixed isotropic temperature factors for the two H atoms. The structure contains zigzag chains of hydrogen-bonded anion tetrahedra that extend in the [010] direction. Each tetrahedron is additionally linked to a tetrahedron in a neighboring chain to give a planar structure with hydrogen-bonded sheets lying parallel to (101). Thermal analysis of the superprotonic transition in Cs_2(HSO_4)(H_2PO_4) showed that the transformation to the high-temperature phase occurs by a two-step process. The first is a sharp transition at 334 K and the second a gradual transition from 342 to 378 K. The heat of transformation for the entire process (~330-382 K) is 44 ± 2 J g^(-1). Thermal decomposition of Cs_2(HSO_4)(H_2PO_4) takes place at much higher temperatures, with an onset of approximately 460 K.

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Haile, Sossina M.0000-0002-5293-6252
Additional Information:Copyright © 2000 International Union of Crystallography. (Received 3 May 1999; accepted 20 July 1999) The authors are pleased to acknowledge the assitance of Dr. Ma Chi with the electron microprobe analysis. This work was funded in part by the National Science Foundation via a National Young Investigator Award to SMH, and in part by the Irvine Foundation. Erratum, Acta Cryst. (2000) B56, 332.
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Irvine FoundationUNSPECIFIED
Subject Keywords:Superprotonic; Conductors; Thermal behavior; Dicesium hydrogensulfate dihydrogenphosphate
Issue or Number:6
Record Number:CaltechAUTHORS:20131125-162530979
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Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:42709
Deposited By: Jonathan Gross
Deposited On:02 Dec 2013 23:28
Last Modified:10 Nov 2021 16:27

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