Effects of Zr/Ce molar ratio and water content on thermal stability and structure of ZrO2–CeO2 mixed oxides prepared via sol–gel process

ZrO2–CeO2 mixed oxides were synthesized via sol–gel process. Thermal stability, structure and morphology of samples were investigated by powder X-ray diffraction, FT-Raman spectroscopy, X-ray photoelectron spectroscopy and scanning electron microscopy. In this approach, the solvent composition and Zr/Ce molar ratio have great influences on the structure and morphology of final products. With decreasing water content in the mixed solvent, specific surface area of powders increased and the single tetragonal phase was obtained. Only when the volume ratio of water and ethanol and the Zr/Ce molar ratio were 1:1, tetragonal t″-Zr0.5Ce0.5O2 could be stabilized in powders at temperature as high as 1000 °C. Meanwhile, tetragonal (t′) and (t″) phases coexisted in Zr0.5Ce0.5O2 solid solution without peak splitting after calcination at 1100 °C, further transforming into cubic and tetragonal (t′) phases at 1200 °C. The effective activation energy for Zr0.5Ce0.5O2 nanocrystallite growth during annealing is about 5.24 ± 0.15 kJ/mol.

Figure optionsDownload as PowerPoint slideHighlights
► Tetragonal t″ phase was stabilized in Zr0.5Ce0.5O2 solid solution at temperature as high as 1000 °C.
► Specific surface area of powders decreased with the increase of water addition and the Ce content.
► The single stable phase was controlled by adjusting the volume ratio of water and ethanol.
► Tetragonal (t″) phase dissociated into cubic and tetragonal (t′) phases at 1200 °C.