Study of Protonic Mobility in CaHPO4·2H2O (Brushite) and CaHPO4(Monetite) by Infrared Spectroscopy and Neutron Scattering

✍ Scribed by L. Tortet; J.R. Gavarri; G. Nihoul; A.J. Dianoux

• Publisher: Elsevier Science
• Year: 1997
• Tongue: English
• Weight: 375 KB
• Volume: 132
• Category: Article
• ISSN: 0022-4596
• DOI: 10.1006/jssc.1997.7383

✦ Synopsis

We report the first quasi-elastic neutron scattering analysis of proton mobility in the solid electrolyte CaHPO 4 • 2H 2 O (brushite). We have studied this hydrated phosphate, in powder state, from 190 to 520 K, using an incident wavelength of 5.12 A s . The time of flight spectra are converted in S(Q, ) structure factor and inelastic frequency distribution P(Q, ) in the energy range 0-200 meV (0-1600 cm) ؊1 . A quasi-elastic contribution is clearly evidenced above room temperature; it is fitted with a jump model, involving hydrogen bonds. The quasi-elastic and inelastic scattering data are compared with FTIR results. Two kinds of motions are determined: jumps of acidic protons on hydrogen bonds and vibrations of lattice water molecules associated with the motion of their hydrogen atom on hydrogen bonds (E +0.145 eV). Above 450 K the dehydration of the compound is accompanied by the appearance of a long-range diffusive motion and by the disappearance of some low-frequency inelastic bands.