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The ESIS Technical Committee for Ceramics (TC6) is running a jointprogram to characterise a commercial silicon nitride ceramic with respect to all propertiesnecessary to a proper design process. In this paper some preliminary results ofmeasurements on the ESIS Reference Silicon Nitride are presented: the room temperature4-pt. bending strength is around 870 MPa and the 3-pt. bending strength is around990 MPa. These two data clearly demonstrate the volume dependence of strength, whichcan consistently be described with the Weibull theory and a Weibull modulus of about 15.The room temperature fracture toughness of the material is 4,9 MPam1/2 (determined withthe SEVNB method). IF-toughness values are between 4,8 to 7,9 MPam1/2. Although somesub-critical crack growth exists at room temperature (the crack growth exponent is around50), severe time dependent damage starts around 1000°C.