Modification of interface anisotropy and its effect on microstructural evolution during ostwald ripening

We performed an experiment to study the role of anisotropy in interfacial energy during the coarsening of a complex oxide CaCu3Ti4O12 (CCTO) material system. When we altered the interface anisotropy, we observed that evolution and sizes of spherical grains completely altered to facetted cubes. When interface became anisotropic, crystal growth appears to occur by the surface attachment/detachment, the motion of ledges, and the nucleation of new layers. Our observations showed that new layers grew by screw dislocation mechanism. This suggests that nucleation limited coarsening is occurring by the development of a transient bimodal grain size distribution consisting of large growing grains with step. In presence of PbO we always observed the development of shaped nucleus which grew larger. Sometimes very complex shaped crystals grew as a metastable shape. These shapes became uniform as the growth progressed and size of grains became larger. This process produces smaller grains that act as a source of material for the growing less defective larger grains.