Investigation of phase and structural states in nanocrystalline powders based on zirconium dioxide

The behavior of a polycrystalline body during sintering ZrO2 is determined not so much by the properties of individual particles but by the properties of aggregates, and the strength of the bonds between powder particles significantly affects the sintering process and the final properties of the ceramic composite materials. An increase in density and a uniform porosity distribution is achieved at such a pressure and sintering temperature when the process of intensive recrystallisation has not yet begun. Conventional sintering at a temperature of 1500 °C with a holding time of 1 h of ZrO2 and ZrO2–20 wt. % Al2O3 samples with an initial particle size of 120 nm and 40 nm, respectively, allowed us to obtain a material with a relative density of 81% (ZrO2) and 86% (ZrO2–20 wt. % Al2O3). The method of electroconsolidation was used to produce bulk samples of submicron ceramics of ZrO2–n wt. % Al2O3 (n = 10; 20; 30) compositions with a density of up to 99% of the theoretical one and a microstructure scale of about 270 nm. It was established that the addition of metastable Al2O3 nanopowders causes a shift in the onset of shrinkage of tetragonal YSZ to high temperatures and affects the reduction of the grain size of tetragonal YSZ to 170–200 nm.