Plastic deformation of ductile ceramics in the Al2TiO5–MgTi2O5 system

Ceramics are typically rigid and brittle. If this brittleness could be overcome, their application can be widely expanded. Itacolumite is known as a highly flexible unique rock in the sandstone group. The microstructure of itacolumite has many narrow gaps at the grain boundaries; these gaps allow a slight displacement of the particles, and the rock can plastically bend when stressed. The authors tried to develop highly ductile ceramics by mimicking itacolumite, which resulted in the Al2TiO5–MgTi2O5 solid solution ceramics. These ceramics have a high ductility and good stress relaxation properties against flexure stress because there are many thin gaps along the grain boundaries formed by discontinuous grain growth during the sintering process and anisotropic thermal expansion during the cooling process. The ductility is caused by the integration of a slight displacement of the grains. This phenomenon was observed as a high-internal friction, reflecting the total friction of a high-grain boundary area.