Proton motions in hydrogen-bonded ferroelectric and antiferroelectric solids. Part 1.—Energy-loss neutron incoherent-scattering spectra of KH2PO4 and Ag2H3IO6 for T < Tc

Abstract

The energy-loss neutron incoherent-scattering spectra for the ferroelectric and antiferroelectric phases of KH₂PO₄ and Ag₂H₃IO₆ respectively are reported in the interval 280–1400 cm^–1. The transverse proton modes have been identified in both ferroelectric solids; the i.-r. spectrum of paraelectric Ag₂H₃IO₆ in the frequency interval 50–1500 cm^–1 has been assigned on the basis of symmetry correlation. An additional mode, which must involve some protonic motion, has been observed at 570 cm^–1 in the low-temperature phase of KH₂PO₄; the PO^–₄ molecular vibrations of KH₂PO₄ are compared with the neutron spectra of K₂HPO₄ in the interval 280–1200 cm^–1.