Investigation of switching dynamics by fitting FGM and NLS models to PVA based NaNO2-CsNO3 composite transients

Abstract

Finite Grain Model (FGM) introduces the concept of grain boundaries lying adjacent to two or more grains in a given ferroelectric crystal. The grain boundaries obstruct the domain growth and hence domain size that may be expected on the basis of Infinite Grain Model. Under the effect of alternating voltage, domains alter their sizes regularly and polarities after specific time intervals that can be correlated with domain switching time. In domain switching studies, the research interest remains in estimation of microscopic parameters like nucleation rate, characteristic time, dimensionality, domain size etc. and besides that to know how the nucleation process progresses. FGM is a statistical model which is successfully used here for investigation of switching dynamics of PVA based NaNO2-CsNO3 mixed system composites optimized for ferroelectric response. This mixed system was formed with CsNO3 mole percent x = 0.09 in optimized equal wt% NaNO2-PVA ferroelectric composite. FGM assumes that nuclei cannot grow unrestrictedly in those ferroelectric thin films which are constituted by elementary regions containing only a few nucleation centers; the switching in one region does not necessarily lead to the switching in another neighbouring region. This is the underlying sense of Nucleation Limited Switching (NLS) model which assumes that switching is carried independently in different regions and it is accomplished in a time depending on the history of growth of that region. The NLS fit over whole range of switching times suggests that composite film can be considered an ensemble of elementary regions individually characterized by independent relaxation times.