Structural model of low-temperature phase transformation and fracture of zirconia-based ceramic material

Abstract

The variation of the structural parameters, including the interplane distanced(III), the amount of tetragonal phaset, and the size of regions of coherent scattering, in the process of the tetragonal-monoclinic transformation in cooling of a ZrO2−Y2O3−Al2O3 ceramic material with a variable phase composition from the sintering temperature (1500–1700°C) is considered. It is established that the dependences of the interplane distancesd(III) on the temperature behave nonlinearly in the temperature range of the phase transformation. It is shown from the data of an x-ray analysis that the tetragonal-monoclinic phase transformation occurs in at least two stages, one of which consists in rhombic distortion of the lattice and the other of which results in formation of a monoclinic phase. The suggested model is used to construct an elementary cell of the monoclinic phase and interpret the fracture behavior of a transformation-toughened ceramic material.