Metastable forms of the tetragonal phase in compositionally homogeneous, nanocrystalline zirconia–ceria powders synthesised by gel-combustion

Abstract

International audienceThe crystal structure of compositionally homogeneous, nanocrystalline ZrO₂–10, 30, 50, 70 and 90 mol% CeO₂ powders synthesised by a pH-controlled nitrate–glycine gel-combustion process has been studied by X-ray diffraction and Raman spectroscopy. All the powders with a CeO₂ content up to 70 mol% exhibited the tetragonal phase (<i>P</i>4₂/<i>nmc</i> space group), whereas the ZrO₂–90 mol% CeO₂ solid solution presented the cubic phase (<i>Fm</i>3^-<i>m</i> space group). The axial ratio <i>c</i>/<i>a</i> decreased with increasing CeO₂ content and became unity for ZrO₂–70 mol% CeO₂ powders. By analysing X-ray diffraction data using the Rietveld method, it was found that this material exhibited the t″-form of the tetragonal phase (the oxygen atoms were displaced from their ideal sites of the cubic phase along the c axis). Raman spectroscopy study confirmed the results found by X-ray diffraction. The morphology of the nanopowders was also evaluated

Temperature effects on structural properties in the synthesis of nanocrystalline Zr0.5Ce0.5O2 solid solution: A study by XRD and HRTEM

“…However, this splitting is not evident in nanosized Zr 0.5 Ce 0.5 O 2 powders, because of the very small particle size and the resulting broad XRD peaks. Nevertheless, a marked asymmetry indicative of such splitting is observed in this peak [11][12][13].…”

“…Several routes have previously been used for the synthesis of compositionally homogeneous nanocrystalline ceria-based solid solutions, including the sol-gel method [7], hydrothermal synthesis [8], the polymerized complex method [9], the amorphous citrate process [10] and gel-combustion [11]. Lamas et al [12] reported a study of the tetragonal-cubic phase transition on nanocrystalline powders obtained by a pH-controlled nitrateglycine gel-combustion method (average crystallite sizes were in the range of 8-20 nm).…”

Structure and thermal properties of heat treated plasma sprayed ceria–yttria co-stabilized zirconia coatings

“…a reduction of the peak intensity, especially at low angles. Bfactors (isotropic temperature factor) were fixed for each element to standard values, without modifying the quality of the fit [25,26].…”

Thermal and physical properties of ZrO2–AlO(OH) nanopowders synthesised by microwave hydrothermal method

“…The production process of ZrO 2 -Al 2 O 3 (ZrO 2 -AlO(OH)) nanopowders follows various chemical routes, such as sol-gel method [4,[18][19][20], hydrothermal synthesis [21,22] or co-precipitation method [23,24]. It was found [25] that the main benefit of hydrothermal synthesis is the generation of weakly agglomerated nanopowder.…”