The Influence of ZrO2-Based Solid Solution Amount on the Physicochemical Properties of Al2O3–ZrO2–Y2O3–CeO2 Powders

M.Ya. Holovchuk 2,

1 I. M. Frantsevich Institute for Problems of Materials Science of the NAS of Ukraine, Krzhizhanovsky str., 3, Kyiv, 03142, Ukraine
2 Karpenko Physico-Mechanical Institute of the NAS of Ukraine, Lviv, Ukraine

Powder Metallurgy - Kiev: Frantsevich Institute for Problems of Materials Science NASU, 2021, #03/04


For the first time, Al2O3-based nanocrystalline powders with different ZrO2 amounts were produced by hydrothermal synthesis in an alkaline medium for designing ZTA composites. In ZTA composites, ZrO2-based solid solution particles codoped with ceria and yttria are dispersed in a rigid Al2O3-based matrix. To examine the variation in physicochemical properties, the 90 wt.% Al2O3–10 wt.% ZrO2 (Y2O3, CeO2) and 58.5 wt.% Al2O3–42.5 wt.% ZrO2 (Y2O3, CeO2) powders were used. The ZrO2-based solid solution had composition 90 mol.% ZrO2–2 mol.% Y2O3–8 mol.% CeO2. The hydrothermal powders were heat-treated in the temperature range 400–1450 oC. The powder properties were studied by X-ray diffraction, differential thermal analysis, and electron microscopy. The powder specific surface area was determined by the BET method. The size of the primary particles was determined by the Scherrer equation. The AMIC software (Automatic Microstructure Analyzer) was used to process the results of morphology. Phase transformations and active sintering of the ZTA powders determined the dependences of the primary particle size and powder specific surface area on the heat treatment temperature. With increasing ZrO2 content, the temperature of   F-ZrO2 → T-ZrO2 phase transformation decreased, the probability of M-ZrO2 formation increased, and the sequence of Al2O3 phase transformations varied after the boehmite decomposition. The variation in morphology and dependence of the powder specific surface area in the heat treatment process indicated that the powders had increased sintering activity. The dependence of the shape factor characterizing the nanocrystalline 90AZG and 58.5AZG powders on the heat treatment temperature was studied. The starting nanosized 90AZG and 58.5AZG powders had similar distribution of agglomerates according to the shape factor. Round agglomerates and multifaceted regular agglomerates were predominant. The regularities of variation in the shape factor with temperature with the topochemical memory effect of the powders were established. The mechanical properties of the samples sintered from the hydrothermal nanocrystalline 90AZG and 58.5AZG powders. With increasing ZrO2 content, the microhardness of the ZTA composites decreased from 195 to 160 MPa, fracture toughness (KIс) increased from 6 to 8 MPa · m0.5, and Vickers hardness decreased from 8.3 to 5.6 GPa. The improvement in consolidation methods for ZTA composites will allow tool, structural, and functional ceramics with the necessary properties to be produced.