Proton conductivity and spontaneous strain below superprotonic phase transition in Rb3H(SeO4)2

Matsuo, Yuichi; Hatori, Junko; Yoshida, Yukihiko; Saito, Keiko; Ikehata, Seiichiro

doi:10.1016/j.ssi.2005.04.047

Cited by 15 publications

(7 citation statements)

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“…Hydrogen-bonded solid acid crystals MH 2 XO 4 (where M = K, Rb, Cs, Tl and X = P, S, Se) exhibit high proton conductivity, often called superprotonic conductivity , at a temperature above a phase transition ( T s ). − This high proton conductivity in the superprotonic phase has attracted interest due to its potential application in fuel cell membranes based on solid electrolytes. , Recently, an increase in proton conductivity at temperatures well below the superprotonic phase transition temperature ( T s ) has been reported in solid acid materials and called the precursor effect . − Despite numerous studies, these phenomena are not well understood and remain a matter of debate. In particular, the superprotonic phase transition at high temperatures has been described by competing models as either a structural transition − or a chemical decomposition with partial polymerization. − Further study is needed to understand the local structure and ion dynamics in these materials so as to resolve this question.…”

Section: Introductionmentioning

confidence: 99%

Investigations of Proton Conduction in the Monoclinic Phase of RbH₂PO₄ Using Multinuclear Solid-State NMR

2009

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To understand the nature of the high-temperature phase transition and the origin of proton conductivity in rubidium dihydrogen phosphate RbH 2 PO 4 , (RDP), we utilized variable-temperature 1 H, 31 P, and 87 Rb MAS NMR at 11.7 and 21.1 T. The variable-temperature 1 H MAS NMR spectra do not show water peaks in the temperature range of 300-400 K, which argues against a partial polymerization and/or decomposition. The 1 H DQ MAS NMR spectra acquired at high field (21.1 T) reveal three different proton sites, and dipolar recoupling experiments give estimates of distances. This evidence supports the formation of a superstructure (doubling of the unit cell along the a-axis) in the high-temperature monoclinic phase. The variable-temperature proton spin-lattice relaxation (T 1 ) reveals significant proton dynamics above 340 K, coinciding with the temperature at which an increase of bulk proton conductivity is reported in monoclinic RDP, but well below the macroscopic phase transition. These precursor dynamics foreshadow the onset of superprotonic conductivity. From variable-temperature 31 P and 87 Rb MAS NMR spectra, it is deduced that significant proton dynamics above 340 K are due to the proton transfer between hydrogen bonds accompanied by reorientation of PO 4 tetrahedra.

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Section: Introductionmentioning

confidence: 99%

Investigations of Proton Conduction in the Monoclinic Phase of RbH₂PO₄ Using Multinuclear Solid-State NMR

2009

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“…Details of the crystal growth are described elsewhere. 10,11) The samples were handled carefully to avoid exposure to moisture, and they were kept in vacuum at room temperature until the measurements. Neutron measurements were carried out at the High Flux Back scattering Spectrometer 12) (HFBS) located at the NIST Center for Neutron Research in the U.S.…”

Section: Methodsmentioning

confidence: 99%

“…Rb 3 H(SeO 4 ) 2 belongs to the second class. 11) We naturally need a common mechanism to explain SPC materials for both classes. It is expected that a thorough comparison of proton dynamics below and above T c will shed some light on the origin of SPC.…”

Section: ¹mentioning

confidence: 99%

Interrelationship between Number of Mobile Protons, Diffusion Coefficient, and AC Conductivity in Superprotonic Conductors, CsHSO₄ and Rb₃H(SeO₄)₂

et al. 2014

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Using quasielastic neutron scattering (QENS), we investigated the proton dynamics for two superprotonic conductors, CsHSO 4 and Rb 3 H(SeO 4) 2. To evaluate the self-diffusion coefficients and the number of mobile protons on both superprotonic and normal phases, we focused on proton dynamics not only in the phase above T c , but also in the phase below T c. In Rb 3 H(SeO 4) 2 , the self-diffusion of protons was observed even below the T c phase. In contrast to popular belief, no large changes in the self-diffusion coefficients were observed across T c. Nevertheless, the increase in the number of mobile protons across T c was about 14.5 times, which was estimated from the integrated intensity of QENS spectra, and this change could not account for the increased magnitude of proton conductivity, which is about 500 times. As a large translational self-diffusion coefficient has not been reported in previous works by QENS experiments, there are still unknown factors that contribute to the Nernst-Einstein relation that need to be discovered.

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“…Since maximum 12 protons and 12 protonic holes are available to generate, the maximum carrier density is estimated to be N = 4.5 × 10 21 (cm −3 ), which is one order of magnitude small in comparison with M 3 H(XO 4 ) 2 [M = K, Rb, Cs, X = S, Se] with a superionic phase. 67,68 Together with the absolute value of σ 1// at 270 K, the minimum mobility (σ 1// / Ne) in Ru-and Rh-salts is estimated to be 8.3 × 10 −3 (cm 2 /Vs), which is a little bit smaller than 1.2 × 10 −2 in Co-salt. These values are smaller than 8 × 10 −2 (cm 2 /Vs) in ice I h , but higher than 3.6 × 10 −3 in free water and 2.6 × 10 −3 in M 3 H(XO 4 ) 2 .…”

Section: B Origin Of the Protonmentioning

confidence: 95%

Eigen-like hydrated protons traveling with a local distortion through the water nanotube in new molecular porous crystals {[MIII(H2bim)3](TMA)·20H2O}n (M = Co, Rh, Ru)

Matsui

Tadokoro

2012

The Journal of Chemical Physics

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In molecular porous crystals {[M(III)(H(2)bim)(3)](TMA)·20H(2)O}(n) (M = Co, Rh, Ru), the structural property of confined water network and the dynamics of mobile hydrated protons have been examined by the measurement of infrared spectrum and microwave conductivity. The water network undergoes first order phase transition from the ice nanotube (INT) to the water nanotube (WNT) around 200 K, while the infrared spectral features for these states are almost equivalent. Consequently, the water molecules in WNT dynamically fluctuate in the vicinity of the regulated position in INT with maintaining the O-O distance. The additional band observed around 2200 cm(-1) reveals the emergence of an Eigen-like protonic hydrate, around which the O-O distance locally shrinks to ~2.56 Å. The microwave conductivity exhibiting activation-type behavior, isotope effect and anisotropy indicates that the water nanotube is a quasi one-dimensional high proton conductor. Together with the neutron experimental results, we have clarified that the proton and protonic hole are generated by the self-dissociation in some water molecules just hydrated to the carboxylate oxygen atom of trimesic acid. The Eigen-like hydrated proton and protonic hole contribute to the intrinsic proton conduction accompanying local distortions. The carrier density dominated by the intrinsic ionic equilibrium is not large, whereas the actual mobility, which is higher than 1 × 10(-2) (cm(2)/Vs), yields the present high proton conductivity.

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Proton conductivity and spontaneous strain below superprotonic phase transition in Rb3H(SeO4)2

Cited by 15 publications

References 15 publications

Investigations of Proton Conduction in the Monoclinic Phase of RbH₂PO₄ Using Multinuclear Solid-State NMR

Investigations of Proton Conduction in the Monoclinic Phase of RbH₂PO₄ Using Multinuclear Solid-State NMR

Interrelationship between Number of Mobile Protons, Diffusion Coefficient, and AC Conductivity in Superprotonic Conductors, CsHSO₄ and Rb₃H(SeO₄)₂

Eigen-like hydrated protons traveling with a local distortion through the water nanotube in new molecular porous crystals {[MIII(H2bim)3](TMA)·20H2O}n (M = Co, Rh, Ru)

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Proton conductivity and spontaneous strain below superprotonic phase transition in Rb3H(SeO4)2

Cited by 15 publications

References 15 publications

Investigations of Proton Conduction in the Monoclinic Phase of RbH2PO4 Using Multinuclear Solid-State NMR

Investigations of Proton Conduction in the Monoclinic Phase of RbH2PO4 Using Multinuclear Solid-State NMR

Interrelationship between Number of Mobile Protons, Diffusion Coefficient, and AC Conductivity in Superprotonic Conductors, CsHSO4 and Rb3H(SeO4)2

Eigen-like hydrated protons traveling with a local distortion through the water nanotube in new molecular porous crystals {[MIII(H2bim)3](TMA)·20H2O}n (M = Co, Rh, Ru)

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Investigations of Proton Conduction in the Monoclinic Phase of RbH₂PO₄ Using Multinuclear Solid-State NMR

Investigations of Proton Conduction in the Monoclinic Phase of RbH₂PO₄ Using Multinuclear Solid-State NMR

Interrelationship between Number of Mobile Protons, Diffusion Coefficient, and AC Conductivity in Superprotonic Conductors, CsHSO₄ and Rb₃H(SeO₄)₂