An asymmetric double-well potential model for structural relaxation processes in amorphous materials

Cage decay, near constant loss, and crossover to cooperative ion motion in ionic conductors: Insight from experimental data

“…One source that have been discussed by many workers comes from relaxation of a distribution of asymmetric double well potentials ͑ADWP͒, which seem to have been seen in glasses without mobile ions, in CKN as well as in glassy ionic conductors. In the model of Gilroy-Phillips, 56 the ADWP contribute a loss with a dependence with a not constant but increasing linearly with temperature. Thus the ADWP contribution possibly can be the NCL observed only at low temperatures.…”

Acoustic behaviour of normal and densified vitreous GeO2

“…With respect to the dynamical mechanisms driving the temperature behaviour of the sound velocity, we can 20 and 220 K and the broad peak observed in the acoustic loss and (iii) a poorly investigated mechanism regulating the positive temperature coefficient observed at even higher temperatures and ascribed to elastic microscopic inhomogeneities [2]. Since the limited temperature interval explored below 20 K prevents any significant evaluation of processes governing the region (i), a quantitative analysis has been carried out for the temperature region above 20 K. It is worth noting that, in addition to the relaxation process, the vibrational anharmonicity is also expected to contribute significantly to the variation of longitudinal sound velocity V l between 20 and 300 K. In the above temperature interval the fractional variation of the sound velocity due to the relaxation process can be expressed by the following relation [16]:…”

“…It results the following expression which accounts for the temperature dependence of the acoustic loss [16]: 1b. It is worth emphasizing that, as already observed in borate glasses [17,18], the relaxation strength C* is more than one order of magnitude larger than the tunnelling strength C; this large difference being associated with a parallel difference between f o and P .…”

Non-Arrhenius Ionic Conductivities in Glasses due to a Distribution of Activation Energies

“…week ending 17 AUGUST 2012 0031-9007=12=109 (7)=075901 (4) 075901-1 Ó 2012 American Physical Society of glass where the ultrasonic attenuation loss peaks were observed to be wider than could be described by a single activation energy [14,15]. Mixtures with compositions 0:5Na 2 S þ 0:5½xGeS 2 þ ð1 À xÞPS 5=2 , where x ranges from 0.0 to 1.0, were prepared from 0:5Na 2 S þ 0:5GeS 2 and 0:5Na 2 S þ 0:5PS 5=2 .…”