Nanodomain Size Distribution in Relaxor Ferroelectrics Determined from Temperature Dependent Raman Scattering Sanju Gupta Electrical and Computer Engineering, University of Missouri-Columbia, 6th St. 303 EBW, Columbia, MO, 65211-2300 ABSTRACT Relaxors (PZN, in particular) is an important class of self-assembled nanostructure composite ferroelectric oxides (or perovskite) materials. The interesting features associated with the nanoregions/nanodomains required to describe these relaxors give rise to the most relevant device related characteristics and peculiar physical properties in these materials. In addition, they possess astronomical property coefficients by themselves or when modified with lead titanate (PT) forming solid solution. In the past, we conducted temperature dependent Raman scattering studies on solid solution (1-x)PZN-xPT relaxors single crystals with varying composition; x = 0.02 and 0.085. These studies were performed to obtain relevant information about lattice/phonon dynamics for matching the application criteria such as electromechanical actuators. We showed that the sharp structural phase transition occurs at or near 460 K which is a first-order transition by fitting two spectroscopic variables in Raman spectra for one of the representative bands occurring at 277 cm -1 . Besides structural phase transition, polarization mechanism for the unpoled (x = 0.02) and poled (x = 0.05) specimens is also investigated to understand the polarization mechanism in relaxors using Raman spectroscopy. The difference in the case of poled specimen is accounted for by the influence of residual electric field. Poling also suggested an enhanced local ordering and the increase in the volume of the polar nano-regions. In the present report, we attempted to determine the nanopolar region size and distribution using the above mentioned temperature dependent Raman spectra. We discuss the most suitable mathematical form of nanodomain size distribution for such inhomogeneous material is log- normal and it is bimodal depending upon the temperature regime besides composition. These studies helped to determine the size distribution of nanoscopic embodiments in relaxor ferroelectrics using Raman spectroscopy as a function of temperature which is a dynamical phenomenon. I. INTRODUCTION In the family of ferroelectrics a group of mixed and disordered “relaxors” have been identified including several complex perovskites, such as PbMg 1/3 Nb 2/3 O 3 (PMN), PbSc 1/2 Ta 1/2 O 3 (PST) and so forth [1, 2]. Due to the effect of configurational or orientational disorder the properties of relaxor ferroelectrics are very different from those of translationally invariant or traditional ferroelectrics [3, 4]. Relaxors are functional materials with self-assembled nanostructures (analogous to semiconductor quantum dots) [5] and are characterized by some of the unusual features including: (a) the simultaneous existence of slow kinetics typical for spin glasses with a very large dielectric constant indicating short- or intermediate-range polar order on the nanometer length scale which can be transformed to true long-range order (i.e. to macroscopic polarization) by a suitable change of composition and applying an external electric field as well; (b) the existence of a frequency-dependent slim hysteresis loop even above the Mater. Res. Soc. Symp. Proc. Vol. 966 © 2007 Materials Research Society 0966-T11-01