Photoluminescence and Raman spectroscopy studies of low-temperature γ-Al2O3 phases synthesized from different precursors

• PL study reveals the presence of Mn4+ only in γ∗-Al2O3 and the absence one in γ-Al2O3.
• PL of F-centers in γ-, γ∗-Al2O3 correlating to the emission of Mn4+ in these phases.
• Raman spectra of γ-, γ∗-Al2O3 demonstrate strong differences in spinal structures.

Spectroscopic features of the local structure of high purity (with the content of impurities <10−3 wt.%) spinel-like γ- and γ∗-Al2O3 phases differing in the unit cell parameters were studied. Samples of these phases were synthesized from crystalline boehmite and nanodispersed pseudoboehmite, respectively. For each of the phases, photoluminescence of transition metal ions and oxygen vacancies – F- and F2-centers – was detected, and Raman scattering spectra were recorded. The photoluminescence study of γ∗-Al2O3 revealed octahedrally coordinated ions Mn4+. Values of the crystal field strength and Racah parameters for Mn4+ ions in γ∗-Al2O3 were determined. Manifestation of PL of Mn4+ ions in γ∗-Al2O3 and its absence in γ-Al2O3 can serve as the indicator for distinguishing between these phases. It was found that γ- and γ∗-Al2O3 samples have individual Raman spectra. The revealed spectroscopic features in the local structure of γ- and γ∗-Al2O3 phases confirm the differences between these spinel-like structures.

Raman and photoluminescence spectra of γ-Al2O3 samples synthesized from crystalline boehmite and nanodispersed pseudoboehmite.Figure optionsDownload high-quality image (143 K)Download as PowerPoint slide