Synthesis, structural characterization and high pressure phase transitions of monolithium hydronium sulfate

Abstract

A three dimensional lithium hydronium sulfate LiSO4 center dot H3O [1], [space group Pna2(1) a = 8.7785(12) angstrom, b = 9.1297(12) angstrom, c = 5.2799(7) angstrom, V = 423.16(10) angstrom(3)] was synthesized via solvothermal methods using 1,5-naphthalenedisulfonic acid (1,5-NSA) as the source of sulfate ions. The structure of [1], determined by single crystal X-ray diffraction techniques, consists of corner sharing LiO4 and SO4 tetrahedra, forming an anionic 3-D open framework that is charge balanced by hydronium ions positioned within channels running along [001] and forming strong H-bonding with the framework oxygen atoms. Compound [1] undergoes two reversible phase transitions, involving reorientation of SO42- ions at pressures of approximately 2.5 and 5 GPa at room temperature, as evident from characteristic discontinuous frequency drops in the v(1) mode of the Raman spectra. Additionally, compound [1] forms dense beta-lithium sulfate at 300 degrees C, as evident from temperature dependent powder XRD and combined reversible TGA-DSC experiments. (C) 2012 Elsevier Inc. All rights reserved.