Avalanches during ferroelectric and ferroelastic switching in barium titanate ceramics

Ferroic switching of 90 ° domains in BaTiO3 can be simultaneously ferroelectric and ferroelastic. Although the general features of their respective ferroelectric and ferroelastic hysteresis loops are similar, the dynamic properties are not. Switching proceeds via avalanches, where changes of the domain structure trigger further nanostructural changes until the avalanches expire and the sample remains in a metastable state. Avalanches are characterized by energy singularities (energy "jerks"), which are power law distributed with an energy exponent ϵ. Using acoustic emission spectroscopy, we find that the energy exponent in ceramics during ferroelectric switching is near the mean field value ϵ∼1.3, whereas stress driven ferroelastic switching is characterized by ϵ∼1.8. This value is much larger than the field integrated mean field value ϵ∼1.66, which was found for ferroelectric switching of single crystals. Thus, BaTiO3 displays three separate dynamical processes for microstructural changes under electric and mechanical stress fields.