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Description
Transitional nano-alumina (TNA) is a promising nanomaterial for catalysis and high-performance composite production. In this work, we report the results of a preliminary study of its thermally induced structural and electronic dynamics. The structure of TNA powder was investigated with the powder X-ray diffraction method. Average particle size and lattice strain were determined by the Sherrer’s approach, Williamson-Hall analysis, and the Halder-Wagner method. Structural studies confirmed the high phase purity of the investigated system and a pronounced nanostructured character. Differential scanning calorimetry measurements are in further support of these findings. Temperature-dependent Raman spectroscopy, in conjunction with two-dimensional correlation analysis techniques, was used to probe the phonon and electron dynamics in TNA. Raman scattering spectra are dominated by a broad photoluminescence (PL) feature spanning the range from 1200 to 4000 cm-1. We attribute this feature to oxygen vacancy–related centers and transition metal impurities. PL intensity exhibits an initial weakly increasing trend from room temperature to about 50 ºC, followed by a very strong thermal quenching from 60 up to 200 ºC. We attribute such behavior to two competing thermal processes, including thermally activated population or activation of an emissive state, along with a thermally activated nonradiative quenching pathway. Quantitative kinetic models for the two processes were derived, and fitting to the experimental temperature-dependent data gives an apparent activation energy for the dominant thermal quenching process of ~ 0.27 eV. This pathway includes thermally assisted charge carrier transfer to nonradiative centers, detrapping, surface-state relaxation, and defect-state conversion.
Keywords: nano-alumina, structural dynamics, photoluminescence, thermal quenching, surface-state relaxation.
| Conference Topics | Nanomaterials and Nanotechnology |
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