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Item Proton-glass dielectric behavior of a Rb0.52(ND4)0.48D2PO4 crystal(1984-09) Schmidt, V. Hugo; Waplak, S.; Hutton, Stuart L.; Schnackenberg, P. T.The c axis dielectric permittivity at 1 kHz was measured for a 71.4 at.% deuterated crystal of Rb0.52(ND4)0.48D2PO4 from 4 to 300 K. The permittivity follows, down to 150 K, a Curie-Weiss law with a Curie temperature of 0 K. Below this temperature the susceptibility rounds off to a broad maximum at 80 K, and below 50 K, starts decreasing rapidly. Between 25 and 40 K, the inverse susceptibility obeys a Curie-Weiss law which extrapolates to zero at 43 K. At 4 K, the relative permittivity flattens out to a value of 11.5. The results show general agreement with predictions of a Landau model giving a second-order transition to an antiferroelectric state at 43 K, but the rounding of the susceptibility peak over a very wide temperature range agrees better with predictions of a model which considers the asymmetry of the typical hydrogen bond caused by the crystal being only partly ammoniated. Permittivity results of Courtens and of Iida and Terauchi for undeuterated crystals with 35% and 60% ammonium, respectively, are also compared with predictions of this second model.Item Brillouin scattering study of the ferroelectric phase transition in tris-sarcosine calcium chloride(1985-01) Hikita, T.; Schnackenberg, P. T.; Schmidt, V. HugoBrillouin spectra from longitudinal phonons in ferroelectric tris-sarcosine calcium chloride 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 the phonons. From the temperature where the linewidth is maximum, the relaxation time of the polarization fluctuations is estimated to be τ=3.1×10−12/(Tc-T) sec, where Tc is the ferroelectric transition temperature. We also observed anomalies in Brillouin shift and linewidth of the [010] phonons which propagate along the ferroelectric b axis. These anomalies are interpreted as coming from electro- strictive coupling. The energy-relaxation time was estimated to be τE=2.5×10−10/(T-Tc) sec in the paraelectric phase and τE=1.0×10−9/(Tc-T) sec in the ferroelectric phase, by comparing our Brillouin results with those of the ultrasonic measurements.