Fracture Toughness Measurements on Zirconia Toughened Ceramics

Three techniques for fracture toughness measurements on zirconia toughened ceramics were evaluated: the notched beam (NB) technique, the indentation fracture (IF) technique and the indentation strength in bending (ISB) technique. Using these techniques comparative measurements were performed on samples prepared by pressing (uniaxial) and sintering of four commercially available powder types. These were: Toyo Soda (Japan) powders with the designations TZ3Y (2,86 mole% Y₂O₃), TZ3YA (2,77 mole% Y₂O₃, 0,1 wt% A1₂O₃) and TZ3Y20A (2,88 mole% Y₂O₃, 20 wt% A1₂O₃) and a powder supplied by viking Chemicals (Denmark) designated as YP5Z-2.5 (2.5 mole% Y₂O₃). The measurementsshowed that similar K_lc values were obtained with the IF- andISB-techniques, which therefore are recommended for K_lcmeasurements. Too high values were, however, obtained with theNB-technique which therefore cannot be recommended. Finally,the measurements showed that a high temperature annealing is recommended prior to testing for the IF-technique.