Brillouin scattering near the ferroelectric phase transition in TSCC

Abstract

Brillouin spectra from longitudinal phonons in ferroelectric tris-sarcosine calcium chloride (TSCC) propagating along [100], [010] and [001] have been measured as functions of temperature. Large anomalies were found in the Brillouin shift and linewidth in the [100] and [001] phonons. These anomalies are interpreted as arising from the linear coupling of the polarization and phonons. From the the temperature where the linewidth is maximum, the relaxation time of the polarization fluctuations is estimated to be τ = 3.1×10⁻¹²/(T_c−T) sec, where T_c is the ferroelectric transition temperature. We also observed anomalies in Brillouin shift and linewidth of the [010] phonons which propagate along the ferroelectric axis. These anomalies are interpreted as coming from electrostrictive coupling. The energy relaxation time was estimated to be τ_E=2.5×10⁻¹⁰/(T−T_c) sec in the paraelectric (PE) phase and τ_E=1.0x10⁻⁹/(T−T_c) sec in the ferroelectric (FE) phase, by comparing our Brillouin results with those f the ultrasonic measurements.