Journal ArticleDOI
On the high-temperature phase transitions of CsH2PO4: A polymorphic transition? A transition to a superprotonic conducting phase?
TLDR
In this paper, X-ray diffraction, TGA, differential scanning calorimetric (DSC), and impedance analysis were used to study the reported high-temperature phase transitions at 107, 149, 230, and 256 °C in crystals of cesium dihydrogen phosphate, CsH2PO4 (CDP).Abstract:
X-ray diffraction, thermogravimetric (TGA), differential scanning calorimetric (DSC), and impedance analysis were used to study the reported high-temperature phase transitions at 107, 149, 230, and 256 °C in crystals of cesium dihydrogen phosphate, CsH2PO4 (CDP). Our results show strong evidence that at all these temperatures, the observed DSC or differential thermal analysis (DTA) endothermic effects appear only as a consequence of a dehydration process starting on the surface of the crystal. Our results thus show that the reported transition at 230 °C is not a polymorphic transition. This means that the monoclinic symmetry, stable at room temperature, with space group P21/m–C2k2, is maintained up to the final decomposition. Moreover, since we have not found any evidence for the existence of a superprotonic high-temperature phase above 230 °C, the high conductivity above 230 °C is thus only a consequence of the dehydration of the crystal surface.read more
Citations
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Solid acid proton conductors: from laboratory curiosities to fuel cell electrolytes
TL;DR: The result indicates that enhancing power output beyond the present levels will require improving cathode properties rather than further lowering the electrolyte thickness, and a discussion of the entropy of the superprotonic transition and the implications for proton transport is presented.
Journal ArticleDOI
Protonic conduction of CsH2PO4 and its composite with silica in dry and humid atmospheres
TL;DR: In this paper, the conductivity of polycrystalline CsH2PO4/silica composite was measured in the temperature range from 150 to 250 °C under a humid condition.
Journal ArticleDOI
High-Temperature Behavior of CsH2PO4 under Both Ambient and High Pressure Conditions
TL;DR: In this article, the high-temperature behavior of polycrystalline poly(H) poly(PO) was examined under both ambient and high pressure (1.0 ± 0.2 GPa) conditions.
Journal ArticleDOI
A review on phosphate based, solid state, protonic conductors for intermediate temperature fuel cells.
TL;DR: In this review, the potential use of phosphate compounds as electrolytes for intermediate temperature fuel cells is summarized and various examples on ammonium polyphosphate, pyroph phosphate, cesium phosphate and other phosphate based electrolytes are presented and their preparation methods, conduction mechanism and conductivity values are demonstrated.
Journal ArticleDOI
Comment on “Does the structural superionic phase transition at 231 °C in CsH2PO4 really not exist?” [J. Chem. Phys. 110, 4847 (1999)]
TL;DR: In this article, single crystal and powder diffraction investigations have revealed that the paraelectric phase of cesium dihydrogen phosphate, CsH2PO4 (CDP), from the crystallographic point of view is stable (space group P21/m) up to ca. 231°C.
References
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Journal ArticleDOI
High temperature phase transitions and proton conductivity in some KDP-family crystals
TL;DR: In this article, the high temperature phase transitions and conductitivity of dihydrogen phosphates and arsenates were investigated in terms of the proton transport model, taking into consideration the migration of protons between normal and interstitial proton sites.
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Hidden nature of the high-temperature phase transitions in crystals of KH2PO4-TYPE : Is it a physical change ?
TL;DR: In this article, it is suggested that the nomenclature high-temperature phase transition (HTPT) around T p should be replaced by that onset of partial polymerization at reaction sites distributed on the surface of solids.
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Crystal structure and ferroelectricity of cesium dihydrogen phosphate CsH2PO4
Yoshiaki Uesu,Jinzo Kobayashi +1 more
TL;DR: In this article, structural and dielectric studies have been performed on CsH2PO4 for scrutinizing the validity of the previously reported structure and it is found that the symmetry in the paraelectric state is not orthorhombic as previously assumed but monoclinic with the space group of C.
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Fast proton transport in crystals with a dynamically disordered hydrogen bond network
A. I. Baranov,Boris V. Merinov,A. V. Tregubchenko,V. P. Khiznichenko,L. A. Shuvalov,N. M. Schagina +5 more
TL;DR: In this paper, the proton migration mechanism via successive proton intrabond jumps and reorientation of the OH groups was studied in the low and high conductive phases of CsHSO4, CsDSO4 and Rb3H(SeO4)2 single crystals.
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Frequency dielectric dispersion in the ferroelectric and superionic phases of CsH2PO4
TL;DR: In this paper, the complex admittance was measured for CsH2PO4 in the frequency range from 30 Hz to 60 MHz and in the temperature range 90-550 K. The domain wall relaxation time was found to decrease anomalously when approaching to Tc.