15587-72-1Relevant articles and documents
Understanding the Mechanism of Ferroelectric Phase Transition in RbHSO4: A High-Pressure Raman Investigation
Bhadram, Venkata Srinu,Narayana, Chandrabhas,Pradhan, Gopal K.,Swain, Diptikanta
, p. 7960 - 7965 (2020)
Previous high-pressure dielectric and diffraction studies on rubidium hydrogen sulfate (RbHSO4) observed ferroelectric phase transition below 1 GPa pressure. We have performed high-pressure Raman spectroscopy studies on RbHSO4 up to a maximum pressure of 5.15 GPa and at ambient temperature to understand the microscopic origin and mechanism of ferroelectric transition. On the basis of the pressure dependence of Raman mode frequencies and their full-width at half-maxima, we observed a transition around a pressure of 0.3 GPa, similar to the ferroelectric transition discovered in dielectric measurements, followed by another transition around 2.4 GPa. These phase transitions are evident from the appearance/disappearance of Raman-active modes and the change in the slope of frequencies with pressures. From the pressure dependence of the S-O and S-OH frequencies, we deduce that HSO4- ion ordering results in ferroelectric phase transition around 0.3 GPa. Further, the transition around 2.4 GPa pressure is associated with significant changes in the stretching and bending vibrational frequencies and indicates a structural phase transition with possible lowering of the crystal symmetry. Interestingly, no significant changes are observed in the Raman spectrum around 1 GPa, at which a phase transition was noticed in earlier X-ray and dielectric studies.
Phase ratios in the M2O-V2O5-SO 3 (M = Rb, Cs) systems and the properties of the compounds formed in these systems
Krasil'nikov
, p. 419 - 423 (2007)
Powder X-ray diffraction and microscopy have been used to study phase ratios of the M2O-V2O5-SO3 (M = Rb, Cs) systems, which model the active component of rubidium-vanadium and cesium-vanadium catalysts for sulf
Synthesis and structure determination of Rb2(HSO4)(H2PO4) and Rb4(HSO4)3(H2PO4) by x-ray single crystal and neutron powder diffraction
Stiewe,Sonntag,Troyanov,Hansen,Kemnitz
, p. 9 - 15 (2008/10/08)
Two new compounds, Rb2(HSO4)(H2PO4) and Rb4(HSO4)3 (H2PO4), were synthesized from aqueous solutions of RbHSO4/RbH2PO4. The compounds were characterized by X-ray single crystal analysis and neutron powder diffraction. For Rb2(HSO4)(H2PO4), room temperature and a low temperature modification were found. According to X-ray crystal structure analysis, the compounds have the following crystal data: Rb2(HSO4)(H2PO4) (T = 298 K), monoclinic, space group P21/n, a = 7.448(3) A, b = 7.552(2) A, c = 7.632(3) A, β = 100.47(3)°, V = 422.1(3) A3, Z = 2, R1 = 0.033; Rb2(HSO4)(H2PO4) (T = 160K), monoclinic, space group P21/c, a = 11.555(3) A, b = 7.536(2) A, c = 9.593(2) A, β = 91.56(2)°, V = 853.0(4) A3, Z = 4, R1 = 0.041; Rb4(HSO4)3(H2PO4), orthorhombic, space group P21212, a = 7.612(6) A, b = 14.795(9) A, c = 7.446(4) A, V = 838.6(9) A3, Z = 2, R1 = 0.045. The compounds have different coordination numbers of rubidium, being 7, 8, 9, or 10 with Rb-O distances from 2.9 to 3.3 A. In all cases there were difficulties in the allocation of sulfur and phosphorus due to the small differences in their radii and scattering factors. All structures are characterized by HSO4- and H2PO4-, or disordered H(x)S/PO4- tetrahedra connected to zigzag chains via hydrogen bridges. These chains are linked by additional hydrogen bonds to a layer-like hydrogen bonding system. (C) 2000 Academic Press.
