This document specifies the test method for the determination of thermal diffusivity from room temperature to at least 1 700 K by the flash method for homogeneous monolithic ceramics with porosity less than 10 %. Flash methods, like laser flash, are applicable to homogeneous isotropic materials with thermal diffusivity values ranging from 0,1 to 1 000 mm2 s-1 within the temperature range from approximately 100 K to 2 300 K. The method described in Annex G describes how to estimate, on the basis of the thermal diffusivity test, the specific heat capacity and the thermal conductivity of homogeneous monolithic ceramics with porosity less than 10 %.