Effect of Heat Treatment on the Structure and Phase Composition of the Nanosized Powder Based on a ZrO2 Solid Solution

The nanosized 90 mol.% ZrO 2 –2 mol.% Y 2 O 3 –8 mol.% CeO 2 powder was produced by hydrothermal synthesis in an alkaline environment and heat-treated in the range 400–1300°C. The powder properties were examined by X-ray diffraction (XRD), SEM and TEM, petrography, and BET. According to the XRD data, a low-temperature metastable cubic ZrO 2 (F-ZrO 2 ) solid solution formed after hydrothermal synthesis. According to the petrography and electron microscopy data, TZrO 2 began to form already in the hydrothermal synthesis process. The F-ZrO 2 → T-ZrO 2 phase transformation was completed in the range 700–850°C. Some T-ZrO 2 particles were characterized by a twin substructure. The T-ZrO 2 unit cell volume monotonically increased from 133.58 · 10 –3 nm 3 to 137.09 · 10 –3 nm 3 and the degree of tetragonality from 1.0033 to 1.0140. No M-ZrO 2 was found to form. The powder specific surface area decreased from 94 to 2 m 2 /g in the heat treatment process. The sizes of primary powder particles (5–10 nm) remained almost unchanged in heat treatment up to 1150°C. The Vickers hardness of the ceramics produced from the powder treated at 850°C was 3.1 GPa and critical fracture toughness factor K Ic was 8.4 MPa · m 1/2 . The preservation of the tetragonal structure (T-ZrO 2 ), which is capable of the martensitic T-ZrO 2 → M-ZrO 2 transformation, and the strength characteristics determined open ways for microstructural design of smart materials, including shape memory ones, in the ZrO 2 –Y 2 O 3 –CeO 2 system.