Influence of the Concentrate of Rare-Earth Elements on the Stabilization of High-Temperature Phases and Properties of the ZrO2–7Y2O3-Based Ceramics

Powders based on the ZrO2–7 wt % Y2O3 system, into which oxides of rare-earth elements (REE)—La, Nd, and Pr—were introduced in the form of the concentrate in an amount from 5 to 15 wt %, are prepared by chemical coprecipitation from inorganic precursors. It is established that an increase in the concentrate content leads to a shift in the temperature maxima of thermal effects into the range of high temperatures from 450 to 505°C. The influence of the annealing temperature in a range of 600–1200°C on the phase transformations of the ZrO2–7% Y2O3–REE systems is investigated using Raman spectroscopy. These studies show that the phase composition of powders includes tetragonal zirconium dioxide ZrO2, regardless of the concentrate content. The influence of the sintering temperature on the compaction of synthesized powders and ceramic phase composition and microstructure is investigated. It is revealed that ceramics with the 10% REE concentrate has the largest compaction rate during sintering, while an increase in the concentrate content to 15% leads to the retardation of compaction during sintering. The largest open porosity at all sintering temperatures is inherent to ceramics with 15% REE. It is noted that a decrease in intensity of the peaks of the Raman spectra and their broadening are observed with an increase in the sintering temperature for the samples with 10 and 15% REE concentrate, which is associated with the formation of the tetragonal modification of another type. The results of atomic force microscopy show that the isolation of a new phase having faceting and layered structure occurs in the structure of ceramics containing 15% REE concentrate after sintering at 1350°C.