Fracture toughness K IC analysis of Co-doped 7YSZ

Co-doped samples of 7YSZ with Yb³⁺, Ce⁴⁺ and Nb⁵⁺ having high porosity are subject to Vickers hardness testing. Fracture toughness K_IC values are obtained by measuring linear and non-linear crack geometries. Three separate means are used to calculate the fracture toughness and to investigate the associated trends. It is confirmed that high amounts of retained tetragonal zirconia improve fracture toughness, while elevated amounts of monoclinic zirconia lower overall fracture toughness. The experimental trend for increasing K_IC is Nb:7YSZ<Yb:7YSZ<7YSZ<Ce:7YSZ; however, this trend is qualitative as the Young's modulus values for different samples are corrected for porosity using an equation that does not generally apply to indentation techniques.