Papers by Keyword: Ferroelastic

Abstract: Interfaces are common microstructures and occur in natural and synthetic materials on the local to mesoscopic lenght scale, like ferroic twin walls or interfaces between amorphous and crystalline material. Individual interfaces can be thin walls extended over a few unit cells or even thicker walls up to several 10000 Å. Walls show distinct physical properties and can therefore influence the macroscopic materials properties considerably. Examples of wall structures and their local features related with ferroic, non-ferroic and biomaterials are presented in this work.

Abstract: Interfaces in martensites and ferroelastic crystals show internal structures which are not simply the interpolation of the two adjacent domains. These structures can influence solitary front propagation as observed for large depinning forces. They also contribute to local pinning of walls when the applied forces are close to the depinning threshold. Under these conditions, walls propagate in jerks and avalanches. Typical depinning is observed for very small forces in single ferroelastic needle domain. It is shown that jerks occur in elastically driven system both for planar walls (D=2) and for needle tips (which represents a line in the three dimensional crystal, D=1). The experimental power law exponents are ~ -2 for the energy exponent for collective avalanches, -1.3 for the elastic response function and -1.8 for an advancing needle domain in LaAlO₃.

Abstract: Ferroelectric/ferroelastic structures exhibit systematic crystallographic distortions below certain phase transition temperatures. Domains, or regions of spatial continuity in such distortions, form in a self-compensating pattern when cooled in the absence of an applied field, forming equal volume fractions of all possible states by uniform selection of crystallographic variants. An applied field (poling) can alter the volume fraction of domains within the ferroelectric phase by switching of the non-preferred orientations, a form of ferroelectric domain texture. When ceramics possess a crystallographic texture prior to inducing domain texture, the two component textures combine multiplicatively to form the complete product texture. Using tape cast bismuth titanate (Na0.5Bi4.5Ti4O15) with an initial crystallographic texture, this paper establishes the quantitative approach for resolving both the component grain and domain textures and describing the complete product texture.