Influence of the concentrate of rare-earth elements on the stabilization of high-temperature phases and properties of ceramics based on ZrO2–7Y2O3

Abstract

Using chemical co-precipitation from inorganic precursors, powders based on ZrO2–7wt.%Y2O3 were obtained. Oxides of rareearth elements (REE) – La, Nd, Pr – were introduced into them in concentrated form from 5 to 15 wt.%. Using differential thermal analysis, it was found that an increase in the proportion of concentrate leads to a shift of the temperature maxima of thermal effects to high temperatures from 450 to 505 °C. The influence of the annealing temperature in the range of 600–1200 °C on the phase transformations of the synthesized powders of the ZrO2–7%Y2O3–REE system was studied through Raman spectroscopy. The results showed that their phase composition consists of tetragonal zirconium dioxide ZrO2 regardless of the concentrate content. The effect of sintering temperature on compaction of synthesized powders, phase composition and microstructure of ceramics was examined. It was found that ceramics with 10 % REE concentrate has the highest compaction speed during sintering, and an increase in the concentrate content to 15 % leads to inhibition of compaction during sintering. Ceramics with 15 % REE had the highest open porosity at all sintering temperatures. It was noted that for samples with 10 and 15 % REE concentrate, with increasing sintering temperature, a decrease in the intensity of the Raman spectra peaks and their broadening is observed. It is associated with the formation of a different type of tetragonal modification. The results of atomic force microscopy showed that after sintering at a temperature of 1350 °C in the structure of ceramics containing 15 % REE concentrate, in contrast to other compositions, a new phase with a faceting and a layered structure was detected.