Effect of point defects on ceramic creep

Abstract

The effect of point crystal-lattice defects of different origin on the creep of ceramic materials at high temperatures and low loads is considered. Experimental data are obtained on densely sintered ceramic specimens of technical purity, which makes it possible to eliminate the effect of pores, the glass phase, and other factors on the one hand and simulate the behavior of actual materials on the other. The main mechanism of deformation under these conditions is diffusion. The deformation of pure materials of stoichiometric composition is determined by the processes of formation and motion of intrinsic thermal defects. With increase in the content of impurity defects and nonstoichiometric defects above some limit the deformation rate is restricted by their mobility. The deformation of actual materials from the standpoint of today’s solid-state theory can be represented by accounting for effective characteristics involving empirical coefficients. The introduction of point defects makes it possible to control the deformability of a densely sintered crystalline ceramic material or such a matrix of a material with a complex composition (with inclusions of pores, a glass phase, etc.).