Superprotonic phase transition in CsH(PO3H)

Calum R I Chisholm, Ryan B. Merle, Dane A. Boysen, Sossina M. Haile*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

18 Scopus citations


High-temperature investigations of the compound CsH(PO3H) (or CsH2PO3, cesium hydrogen phosphite) revealed that this material undergoes a transition, with an onset of 137°C, to a phase of high proton conductivity. The transition is accompanied by a large heat of transformation, ΔH = 58 ± 2 J/g (12.4 ± 0.4 kJ/mol), and exhibits measurable hysteresis, occurring at 96°C upon cooling. High-temperature x-ray powder diffraction showed that the high-temperature phase is cubic, with ao = 4.896(1) Å, and likely takes on a CsCI structure, with Cs atoms at the corners of a simple cubic unit cell, and PO3H groups at the center. The conductivity in the high-temperature phase at 160°C is 5.5 × 10-3 Ω-1 cm-1, and the activation energy for proton transport is 0.40 ± 0.01 eV. These values suggest that proton transport is facilitated by rapid PO3H group reorientations in the cubic phase of CsH(PO3H), as is known to occur in the high-temperature, tetragonal phase of CsHSO4.

Original languageEnglish (US)
Pages (from-to)3889-3893
Number of pages5
JournalChemistry of Materials
Issue number9
StatePublished - Sep 1 2002

ASJC Scopus subject areas

  • Chemistry(all)
  • Chemical Engineering(all)
  • Materials Chemistry


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