13774-16-8Relevant articles and documents
High-Temperature Phase Transition in RbH2PO4
Komukae, Masaru,Kawashima, Kazuhiro,Osaka, Toshio
, p. 2076 - 2081 (2000)
Dielectric and thermal measurements were carried out for the RbH2PO4 crystal belonging to the tetragonal system at room temperature. The RbH2PO4 crystal, which could be obtained by heating the tetragonal RbH2PO4 crystal above the tetragonal-monoclinic transformation temperature, undergoes successive phase transitions at 390.1 K and 248.8 K. The tetragonal-monoclinic transformation is accompanied by a rearrangement of hydrogen bonds, namely, a change from a three-dimensional network of hydrogen bonds in tetragonal RbH2PO4 to a two-dimensional network in monoclinic one. The tetragonal space group I42d changes to the monoclinic P21/c by passing through the transformation temperature.
Neutron diffraction study of ferrielectric phase transition in monoclinic RbD2PO4
Magome, Eisuke,Komukae, Masaru,Machida, Mitsuo
, (2007)
Crystal structures of monoclinic RbD2PO4 were studied at 297K in the ferrielectric phase (phase III) and at 350 K in the paraelectric phase (phase II) by means of the single crystal neutron diffraction. The oxygen and deuterium atoms associated with the hydrogen bonds along the b axis are ordered in phase III and are disordered in phase II. Other atoms are ordered in both phases II and III. There are four kinds of PO4 tetrahedra in phase III. The ferrielectricity of phase III were confirmed in the present neutron structural analysis. The III-II phase transition is caused by an order-disorder of PO 4 tetrahedra accompanied by the motion of deuterium atoms within the hydrogen-bond chain. Fluctuations of the oxygen and deuterium atoms related hydrogen-bond chains along the b axis give rise to a quasi-one-dimensionality. 2007 The Physical Society of Japan.
Calve, N. le,Romain, F.,Limage, M. H.,Novak, A.
, p. 131 - 148 (1989)
New rubidium zinc hydrogen phosphate, Rb2Zn2(HPO4)3: Synthesis, crystal structure, and 31P single-crystal NMR
Jensen, Torben R.,Hazell, Rita G.,Vosegaard, Thomas,Jakobsen, Hans J.
, p. 2026 - 2032 (2000)
A new rubidium zinc hydrogen phosphate, Rb2Zn2(HPO4)3, is prepared by an unusual method utilizing long nucleation times. This material is crystallized from a gel with an initial composition of 1.0 ZnO/0.94 P2O5/0.96 Rb2O/0.04 Li2O/41 H2O, while the phosphate concentration equals 1.6 M and pH = 3.5. The gel is placed in a sealed Pyrex flask at 52 °C, and after 4.5 months crystallization of Rb2Zn2(HPO4)3 is noticed. This new crystalline compound has a three-dimensional framework structure built from spiral chains of alternating PO4 and ZnO4 tetrahedra connected pairwise and assembled by other PO4 tetrahedra, rubidium ions, and hydrogen bonds. The two rubidium ions, Rb(1) and Rb(2), have an exceptionally low number of oxygen contacts in the first coordination sphere, five and seven, respectively. Crystal data: Monoclinic, P21/c (no. 14), a = 12.5880(4), b = 12.7170(8), c = 7.5827(8) A, β = 96.100(1)°, Z = 4. A single-crystal 31P NMR investigation of Rb2Zn2(HPO4)3 was performed employing a two-axis goniometer probe and reveals the presence of three chemically and six magnetically nonequivalent phosphorus sites, in accordance with the crystal structure. 31P chemical shielding anisotropies and isotropic chemical shifts (-3.3(3), -2.6(3), and 2.0(3) ppm) have been determined for the three phosphorus sites.
A humidity-controlled precipitation technique enabling discovery of Rb3(H1.5PO4)2
Sanghvi, Sheel,Haile, Sossina M.
, (2021)
The previously unknown compound Rb3(H1.5PO4)2 is successfully synthesized here using a newly developed variant of aqueous precipitation crystal growth. The approach exploits the phenomenon of boiling point elevation in concentrated solutions. Crystals of the title compound were obtained upon heating a stoichiometric solution from 110 to 150 ?°C under a high steam partial pressure of 0.83 ?atm. Single crystal X-ray diffraction studies revealed Rb3(H1.5PO4)2 crystallizes in space group C2/m and is isostructural to Cs3(H1.5PO4)2. As evidenced by thermal analysis, Rb3(H1.5PO4)2 does not undergo a phase transition to a trigonal superprotonic phase upon heating. Even under a steam partial pressure of 0.82 ?atm, under which dehydration is suppressed to a temperature of 263 ?°C, no polymorphic transition is detected. The behavior parallels that of Cs3(H1.5PO4)2 and contrasts that of several structurally and chemically similar selenate compounds. The crystal growth approach developed here may prove particularly useful for obtaining water soluble compounds which are thermodynamically or kinetically disfavored at temperatures close to ambient.
High-temperature thermal behaviors of XH2PO4 (X = Cs, Rb, K, Na) and LiH2PO3
Li, Zikun,Tang, Tongbor
, p. 59 - 64 (2010/07/04)
XH2PO4 ionic compounds have emerged as a viable electrolyte for intermediate temperature fuel cells, and here have been subjected to thermal analysis to clarify their high-temperature properties. Thermoanalytical peaks were identified at 231.5, 239 and 349 °C for CsH2PO4; 127, 250 and 354 °C for RbH2PO4; 232, 270 and 319 °C for KH2PO4; 223, 330 and 352 °C for NaH2PO4; also, 195 and 220 °C for LiH2PO3 (peak temperature values as measured at the same heating rate of 10 K/min). The thermal events at 231.5 °C in CsH2PO4 and 127 °C in RbH2PO4 were previously interpreted as thermal decomposition by numerous researchers, but we confirm their origin in structural phase transition. The high-temperature variations in KH2PO4 and NaH2PO4 are entirely due to thermal dehydration rather than phase transition. We have also examined LiH2PO3, and found, for the first time, an endothermic peak at 195 °C, and attributed it to structural phase transition.
