Dielectric noise spectroscopy of relaxor ferroelectrics
"This thesis attempts to answer one simple question: are the dynamics of relaxor ferroelectrics cooperative? To accomplish this task, we have developed a promising new technique that is excellent at sorting out the internal dynamics of high dielectric materials. Specifically we have examined the dynamics of the relaxor ferroelectric material PLZT(B/65/35) in the ""frozen"" state. A relaxor ferroelectric is a material which has local ferroelectric order on the 1 Onm scale (nanodomains) but on longer scales the material is disordered. The nanodomains appear to go through a freezing transition and it is not known whether this is a cooperative effect. DNS examines the details of the polarization fluctuations from a mesoscopic capacitor, our smallest capacitor has an effective volume of 2x1Q-12cm3, or 107 nanodomains. From the statistical details, the lack of any non-Gaussian noise in this case, we are able to set an upper limit on the number of nanodomains that can act cooperatively in both equilibrium and near equilibrium."
dielectric noise, relaxor ferroelectrics, PLZT(B/65/35), mesoscopic capacitor
University of Illinois - Urbana-Champaign
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