Brillouin-Scattering Study of the Ferroelectric Transition in KH2PO4

Abstract

The Brillouin-scattering spectrum of K${\mathrm{H}}_2$P${\mathrm{O}}_4$ has been studied over the temperature range $118°\mathrm{K}<T<\mathrm{}300\mathrm{}°\mathrm{K}$ with particular emphasis on the region close to the ferroelectric transition at 122°K. Results in the paraelectric phase are analyzed in terms of the piezoelectric coupling of the acoustic $X_y$ shear mode to the ferroelectric soft mode. Results in the ferroelectric phase indicate that the transition is better described by the Slater-Takagi-Senko model than by Cochran's model.