Key insights on the structural characterization of textured Er2O3–ZrO2 nano-oxides prepared by a surfactant-free solvothermal route
| Autor: | Beatriz Julián-López, Purificación Escribano, Francisco Gonell, Verónica de la Luz, Miguel López-Haro, Eloisa Cordoncillo, José J. Calvino |
|---|---|
| Rok vydání: | 2012 |
| Předmět: |
Materials science
HRTEM Structural resolution Mechanical Engineering Metals and Alloys Nanoparticle Crystal growth Nanotechnology Crystal structure Solvothermal route Fluorite Nanocrystalline material Crystal symbols.namesake Chemical engineering Mechanics of Materials Materials Chemistry symbols Er2O3–ZrO2 Thermal analysis High-resolution transmission electron microscopy Raman spectroscopy |
| Zdroj: | Repositori Universitat Jaume I Universitat Jaume I |
| Popis: | Zirconia-mixed oxides can exhibit cubic fluorite and pyrochlore structure. Their discrimination is not easy in nanooxides with a crystal size close to that of a few unit cells. In this work, high resolution transmission electron microscopy (HRTEM) has been employed to provide key insights on the structural characterization of a nanometric and porous mixed Er 2 O 3 –ZrO 2 oxide. The material was prepared by a simple template-free solvothermal route that provided nanocrystalline powders at low temperature (170 °C) with spherical morphology, and high surface area (∼280 m 2 g −1 ). The porosity was mainly originated from the assembling of organic complexing agents used in the synthesis to limit the crystal growth and to control hydrolysis and condensation reaction rates. The samples were characterized by thermal analysis, X-ray diffraction, scanning electron microscopy and N 2 adsorption measurements. A detailed study by HRTEM was conducted on microtomed samples. It was observed that the material was made of nanocrystals packed into spherical agglomerates. HRTEM simulations indicated that it is not possible to identify the pyrochlore phase in nanoparticles with diameter below 2 nm. In our samples, the analysis of the HRTEM lattice images by means of fast Fourier transform (FFT) techniques revealed well defined spots that can be assigned to different planes of a cubic fluorite-type phase, even in the raw material. Raman spectroscopy was also a powerful technique to elucidate the crystalline phase of the materials with the smallest nanoparticles. HREM and Raman results evidenced that the material is constituted, irrespective of the temperature of the final calcination step, by an ensemble of randomly oriented nanocrystals with fluorite structure. This study opens new perspectives for the design of synthetic approaches to prepare nanooxides (fluorites and pyrochlores) and the analysis of their crystalline structure. |
| Databáze: | OpenAIRE |
| Externí odkaz: |
|