Anisotropic sintering shrinkage in alumina ceramics containing oriented platelets

The effect of oriented alpha-Al2O3 platelets on densification and shrinkage behavior of tape-cast alpha-Al2O3 during solid-state sintering was studied using dilatometric sintering shrinkage experiments and microstructural characterization. Platelet-free alumina samples exhibit isotropic shrinkage with an similar to 17% linear final shrinkage. The addition of platelets retards densification, and results in anisotropic shrinkage. Initially during sintering, shrinkage is isotropic for platelet-containing systems; however, it becomes highly anisotropic by inhibition of shrinkage in the platelet orientation direction. In the 10 vol% platelet-containing system, shrinkage was similar to 12% in the casting and the transverse directions and similar to 20% in the direction perpendicular to the casting plane.