Vogel-Fulcher freezing in relaxor ferroelectrics

Phase Transitions in Relaxor Ferroelectrics

This paper covers the properties of relaxor ferroelectrics and considers the transition from the paraelectric state to the relaxor state comparing experimental data with the spherical random-bond randomfield model (SRBRF). It found that this model predicts and is experimental verifies a glassy state at the transition temperature for E < Ec and a ferroelectric state with quench random fields for...

0 Dynamics of relaxor ferroelectrics

We study a dynamic model of relaxor ferroelectrics based on the spherical random-bond—random-field model and the Langevin equations of motion written in the representation of eigenstates of the random interaction matrix. The solution to these equations is obtained in the long-time limit where the system reaches an equilibrium state in the presence of random local electric fields. The complex dy...

Local Ordering in Pb-based Relaxor Ferroelectrics

Anisotropic nonlinear dielectric response of relaxor ferroelectrics

The anisotropy of the nonlinear static dielectric response of inorganic relaxor ferroelectrics of lead magnesium niobate PMN type is studied in the framework of the spherical random bond–random field model. Assuming that the shape of a polar nanoregion PNR and thus its dipole moment is modified by the action of homogeneous lattice strains, the anisotropic part of the interaction between the PNR...

Vogel-fulcher Law of Glass Viscosity: a New Approach

Starting with an expression, due originally to Einstein, for the shear viscosity η(δφ) of a liquid having a small fraction δφ by volume of solid particulate matter suspended in it at random, we derive an effective-medium viscosity η(φ) for arbitrary φ which is precisely of the Vogel-Fulcher form. An essential point of the derivation is the incorporation of the excluded-volume effect at each tur...