Porous ceramics have been studied obtained from ultra-fine zro 2 powders. the porosity of ceramic samples was from 15 to 80%. the structure of the ceramic materials was a cellular structure. A distinctive feature of all the deformation diagrams obtained in the experiment was their nonlinearity at low deformations which was described by the parabolic law. it was shown that the observed nonlinear elasticity for low deformations on deformation diagrams is due to mechanical instability of the cellular elements in the ceramic carcass.