Surface state defining factors as key to the strength of ceramic micro parts

The mechanical properties of ceramic parts are strongly influenced by the quality of the surface. In the present work it is demonstrated that for the surface quality, material specific properties (sintering activity, grain morphology) as well as process-related factors (debinding and sintering) are vitally important. For the exemplarily investigated materials zirconium dioxide (ZrO2) and silicon nitride (Si3N4) the surface morphology of micro specimens turned out to be the limiting factor for high bending strength. Due to its fine and homogenous microstructure ZrO2 allows the formation of very smooth surfaces with correspondingly high characteristic strength up to 3,000 MPa. Si3N4 is characterized by a highly anisotropic microstructure, pronounced grain growth, and thereby high surface roughness. Although both materials reveal virtually the same strength level in macro dimensions, in micro dimensions Si3N4 seems to be the inferior choice with a maximum strength of 1,200 MPa.