Crossover from Ordinary Ferroelectric to Relaxor State: A Pre-Transitional Martensitic Transformation.

In this work we have investigated the nature of the crossover from the ordinary ferroelectric to the relaxor state in (Pb 1 - x Ba x )(Zr 0.65 Ti 0.35 )O 3 ceramics through dielectric and structural characterizations. Based on the martensitic transformation concepts, it is proposed that the continuous addition of isovalent-ions in the normal ferroelectrics decreases the long-range elastic interaction, thus transforming the domain patterns from a micrometer polydomain structure, through single domains, to nanometer polar “tweed” structures with glasslike behavior, which are in turn strongly driven by defects. The electrical interaction between these weakly-coupled polar-tweed structures leads to a wide spectrum of relaxation times, thus resulting in a dielectric relaxation process. [ABSTRACT FROM AUTHOR]