Micro-Brillouin scattering study of ferroelastic phase transitions in KSc(MoO4)(2) - art. no. 144101

High-resolution micro-Brillouin scattering studies of ferroelastic KSc(MoO4 )(2) have been performed in the temperature range 293-125 K giving informat ion about the temperature dependence of the acoustic phonons propagating in the [100], [010], and [001] directions. Strong anomalies in sound velocity and attenuation have been observed for the sound waves corresponding to th e c(11), c(44), and c(66) elastic constants. These results indicate a (3) o ver barm-->2/m improper ferroelastic transition at 260 K followed by two tr ansitions into other ferroelastic and monoclinic phases at 240 and 180 K. T he comparison of the observed anomalies with the results of phenomenologica l theory suggests the following phase transition sequence in KSc(MoO4)(2): P (3) over bar m1-->C2/c -->C2/mC2/c. The present results suggest that belo w 260 K a simultaneously ferroelastic and incommensurate phase may exist, i n agreement with the previous reports.