Fracture toughness of yttria-stabilized cubic zirconia (8Y-CSZ) doped with pure silica

In yttria-stabilized cubic zirconia, the addition of 0.15-5 mass% pure silica introduces a glass phase dispersing uniformly along grain-boundary facets and Lit multiple junctions. For a grain size of 0.75 or 1.7 mum, the dispersion of the glass phase decreases the clastic modulus. the Vickers hardness and the elastic modulus-to-hardness ratio, whereas it affects little in the value of fracture toughness measured by an indentation method. The latter result arises because the decrease in the elastic modulus-to-hardness ratio is compensated by a decrease in the crack length for a given indentation load. Inspection of crack-propagation paths indicates that the glass phase with sizes smaller than those of the matrix grains is not a site for easy crack-propagation, hut provides a site for a crack-deflection mechanism.