Study of the effect of variation of thermal annealing conditions on the structural ordering and phase formation processes in ZrO₂ – Al₂O₃ ceramicss

Interest in composite refractory ZrO2 – Al2O3 ceramics is due to the great prospects for their use in extreme conditions (radiation exposure, thermal cycling, exposure to aggressive environments) due to the high resistance to external influences of these ceramics. Moreover, the features of high resistance to external influences for this type of ceramics are due to their structural features and phase composition, which are controlled by the synthesis method and its conditions. This paper presents the results of studying the influence of variations in the annealing temperature of ZrO2 – Al2O3 ceramics obtained by solid-phase synthesis, as well as establishing the effect of variations in the phase composition on strengthening and resistance to thermal cycling. In the course of the research, using the X-ray phase analysis method, it was found that at temperatures above 1200 °C, the formation of an impurity substitution phase of the AlZrO2 type is observed, the formation of which leads to strengthening and increased resistance to external influences. For ZrO2 – Al2O3 ceramic samples, in which the AlZrO2 phase content was about 15-20 % (samples obtained at annealing temperatures of 1400 – 1500 °C), the change in strength characteristics after 5 successive cycles was less than 3 %, which is more than 9 times lower than the similar change for two-phase samples obtained at an annealing temperature of 1000 °C.