Fabrication and nanoindentation characterization of MgAlON transparent ceramics

Highly transparent MgAlON ceramics were fabricated by pressureless presintering and hot isostatic pressing. The deformation, hardness and fracture toughness of MgAlON transparent ceramics have been studied by nanoindentation technique. The indentation tests were performed with applied loads of 2-400 mN to investigate the variation in mechanical behaviors. It was found that the plastic deformation component dominated MgAlON ceramics at the applied loads from 2 mN to 200 mN. The resistance to plastic deformation decreased when the applied load increased. However, the micro-cracks induced by nanoindentation have been observed at the load above 200 mN. In addition, the true hardness (∼13.5 GPa) was determined based on the proportional sample resistance (PSR). Furthermore, the fracture toughness (2.2-2.7 MPa m1/2) was evaluated using Laugier's equation. This study lends credible the realization of mechanical properties of the MgAlON transparent ceramics in the design and practical applications.