Segregant enhanced fracture of mechanics

The fracture toughness and failure mode of ceramic materials are highly sensitive to the presence of impurities at grain boundaries. Magnesium oxide serves as a model material to investigate fracture with respect to impurity levels at grain boundaries. Lithium fluoride, added to MgO as a sintering aid, is retained as an intergranular phase. By post-fabrication heat treatment, the LiF is removed and a change in fracture mode follows. Transmission and scanning electron microscopy, along with analytical (atomic absorption spectroscopy and selective electrode analysis) and microanalytical (scanning Auger microprobe) techniques are used to follow the progression of LiF with heat treatment. The results of this study are compared to other oxides and carbide systems in which the fracture toughness has also been found to be sensitive to the amount and location of segregants.