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 (Pb1-xBa,)(Zr0.65Ti0.35)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.