High-temperature phase behavior in the Rb 3H(SO 4) 2-RbHSO 4 pseudo-binary system and the new compound Rb 5H 3(SO 4) 4

Chatr Panithipongwut, Sossina M. Haile*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

9 Scopus citations


The high temperature behavior of the pseudo-binary system Rb 3H(SO 4) 2-RbHSO 4 has been investigated through a combination of thermal analysis, high-temperature X-ray powder diffraction and high-temperature electrical impedance measurements. The studies reveal the existence of a new high-conductivity phase, Rb 5H 3(SO 4) 4, that becomes stable at a temperature between 25 and 140°C and is isostructural to a recently reported trigonal phase of Cs 5H 3(SO 4) 4 [M. Sakashita, et al., Solid State Ionics (2007) 178 1262-1267]. Refinement of the Rb structure in space group P3-m at 160°C yields a = 5.9298(2) Å, c = 14.4736(6) Å, V = 440.74(3) Å 3, with Z = 1 and ρ = 3.0691(2) Mg/m 3. At 185°C the compound undergoes an apparently polymorphic transformation with a heat of transition of 14.9 kJ/mol and a slight additional increase in conductivity. No further anomalies are observed up to the highest measurement temperature of 220°C. Compositions rich in Rb 3H(SO 4) 2 relative to Rb 5H 3(SO 4) 4 show, in addition to the polymorphic transformation of the latter, the disproportionation reaction of the former into Rb 2SO 4 and Rb 5H 3(SO 4) 4 at 205°C. Compositions rich in RbHSO 4 display an additional conductivity anomaly at 170°C, which is tentatively assigned to a polymorphic transformation in RbHSO 4.

Original languageEnglish (US)
Pages (from-to)53-57
Number of pages5
JournalSolid State Ionics
StatePublished - Apr 16 2012


  • A.C. impedance spectroscopy
  • Pentarubidium trihydrogen tetrasulfate
  • Phase diagram
  • Rb H (SO )
  • Rb H(SO )
  • RbHSO
  • Rubidium hydrogen sulfate
  • Solid acid
  • Trirubidium hydrogen disulfate
  • X-ray diffraction

ASJC Scopus subject areas

  • General Chemistry
  • General Materials Science
  • Condensed Matter Physics


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