Abstract:

The effect induced by the presence of a polaron related relaxation process on the dielectric properties of a ferroelectric KTa1-xNbxO3 (KTN) crystal was investigated (10(-2)-10(6) Hz, at 300-375 K) using broadband dielectric spectroscopy. Characterization of the process using just the standard frequency domain dielectric parameters can nonetheless provide penetrating insight into its nature and origins. The three parameters, namely: relaxation time (tau), Cole-Cole loss broadening (alpha), and dielectric strength (Delta epsilon) provide each one in its own way, much useful and often overlooked information. The Activation Energy along with the Meyer-Neldel dependance, both extracted from tau serve to illuminate the dynamic properties. At the same time, alpha and especially the combined alpha(ln tau) relationship, expose the fractal structure of the underlying landscape. Finally, the static parameter. Delta epsilon, enables quantification of the dipolar correlations. Hydrostatic pressure (up to 7.5 kbar) was applied to gently perturb the system and observe the outcome on all of the various parameters. This additional degree of freedom allows for a much more comprehensive exploration of the phase space behavior of the system.