High temperature properties of Rb3H(SO4)2 at ambient pressure: Absence of a polymorphic, superprotonic transition

Cowan, Lisa A.; Morcos, Riham Michelle; Hatada, Naoyuki; Navrotsky, Alexandra; Haile, Sossina M.

doi:10.1016/j.ssi.2008.02.016

Cited by 26 publications

(29 citation statements)

References 30 publications

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“…The crystals achieve their superionic state through a structural phase transition at T S , except for Rb 3 H(SO 4 ) 2 , which undergoes a phase separation at the temperature of transformation to the high conducting state [5]. The salts also, except Rb 3 H(SO 4 ) 2 [6], are ferroelastic below T S , so T S ¼ T C and they undergo structural phase transition from the low temperature space group C2/c to the high temperature one R3m.…”

Section: Hydrogen Sulphates and Selenates -Solid Acidsmentioning

confidence: 99%

Anhydrous proton conductors for use as solid electrolytes

et al. 2010

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Anhydrous proton conductors in which proton transport proceeds via structure diffusion are interesting alternatives for membrane materials in hydrogen/air fuel cells. Understanding the mechanism of proton diffusion in candidate materials is necessary to improve their performance. We present the results of our studies of two classes of proton conductors in which conductivity does not rely on the presence of water molecules in their structure: crystalline hydrogen sulphates and selenates and new salts of nitrogen-containing heterocyclic molecules combined with a series of dicarboxylic acids. In the former group, superprotonic conductivity results from a high molecular dynamics of S/SeO 4 groups, which creates an excess of structurally equivalent positions for protons. Ferroelastic properties of the crystals determine their physical behaviour at high temperatures. In particular, ferroelasticity makes a smooth and reversible character of superionic phase transition possible. In the second group of materials, the heterocycles exhibit extensive specific interactions that result in a fluctuating network of H-bonds. Thus, the proton conduction in these materials depends on the number of protons, which can be involved in the diffusion and on the fluctuation rate of the hydrogen bond network.

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Section: Hydrogen Sulphates and Selenates -Solid Acidsmentioning

confidence: 99%

Anhydrous proton conductors for use as solid electrolytes

et al. 2010

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“…The diameter of the semicircle corresponds to the resistance of the sample R. We could not measure the form factor A, where conductivity σ = A / R, since the sample has a complicated shape. Thus, the form factor was estimated from the resistance at ambient pressure, which was extrapolated from the pressure dependence of the resistance, using the literature's conductivity at ambient pressure [7]. The Raman spectra were measured by a SPEX270M single monochromator with a liquid-nitrogen cooled CCD detector.…”

Section: Methodsmentioning

confidence: 99%

“…In particular, the pressure-temperature phase diagrams for the HT, RT, and high pressure (HP) phases of Rb 3 H(SeO 4 ) 2 and (NH 4 ) 3 H(SO 4 ) 2 are quite similar [5]. Trirubidium hydrogen bisulfate (Rb 3 H(SO 4 ) 2 ), which belongs to one of the M 3 H(XO 4 ) 2 families and has the C2/c structures (phase II) at room temperature [1], has an undetermined state (phase IV) at high temperature and ambient pressure [6,7]. However, another high temperature phase (phase I) appeared under high pressure [6].…”

Section: Introductionmentioning

confidence: 99%

Changes in structure and proton conductivity at II–III phase transition of Rb3H(SO4)2

et al. 2010

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“…The 1 H static NMR spectra indicate that both NH 4 + ions and the acidic protons undergo translational diffusion [22]. From the analysis of 1 H T 1 results we have obtained parameters for the translational diffusion of the acidic protons, as listed in [19]. The structure of the high-temperature phase of Rb 3 H(SO 4 ) 2 is not established yet, and it might be different from those of [(NH 4 )1− x Rb x ] 3 H(SO 4 ) 2 (0≤x b 1).…”

Section: Proton Diffusion In Phase Imentioning

confidence: 99%

“…Rb 3 H(SO 4 ) 2 also shows a phase transition at 495 K and indicates a high proton conductivity in the high-temperature phase [17,18]. The presence of a superprotonic phase transition in Rb 3 H(SO 4 ) 2 is controversial [19], because the structure of the high-temperature phase is not established. The mixed-cation [(NH 4 ) 1 − x Rb x ] 3 H(SO 4 ) 2 crystals show a superprotonic phase transition, and the transition temperature is very sensitive to NH 4 -Rb substitution [17,20].…”

Section: Introductionmentioning

confidence: 99%