Raman Scattering Study on the Phase Transition Dynamics of Ferroelectric Oxides

Abstract

Raman scattering spectra of internal modes have been studied in antiferroelectric NH4H2AsO4 at several temperatures near the transition temperature TN. The evidence of the C1 local site symmetry of H2AsO44– in the paraelectric phase has not been obtained even just above TN. The integrated intensity of the v2 mode giving the justification of the C1 symmetry in the antiferroelectric phase increases with decreasing temperature below TN. In addition, the linewidth of the v1 internal mode increases with increasing temperature. From the latter two results, the relaxation of the rigid ice constraint is proposed in the discussion of the models of the phase transition in hydrogen bonded antiferroelectrics. © 1988, THE PHYSICAL SOCIETY OF JAPAN. All rights reserved.