The crack propagation resistance of the materials was measured on notched specimens with a thickness W ranging from 3.5 mm to 5 mm depending on the height of the sintered disc. The ratio of the notch depth on the specimen height a/W was set to 0.4. The notches were made in two steps, first a pre-notch was prepared with a diamond saw with a thickness of 300 µm. Then, this notch was refined with a razor blade and a diamond paste containing 1 µm particles in order to have a notch tip radius with a curvature of about 20 µm. The loading was done at a constant displacement rate of 10 µm/min. The stress intensity factor KJ was determined during stable crack using the J-integral method exposed in ASTM-E1820 standard . Crack length ∆a were indirectly determined by the method of mechanical compliance, described for example in , which allows the calculation of an equivalent crack length by projecting the actual crack length on the axis of the notch. This method, although approximate in our case because there is significant crack deviation, allows the calculation of the initiation toughness KJ 0 , a parameter which is not affected by sample size effect . This allows to compare these results with other publications that have used this method [15].