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Raman and luminescent bands in Y2O3 powders

For decades yttrium oxide has been an important material in ceramic industry, but its role in the first synthesized ceramic superconductor, about fifteen years ago, is something unique. In high purity powdered yttria samples luminescent bands which outnumber Raman bands of cubic yttrium oxide were observed. The influence of different processes such as heating, moisturizing and ball milling to luminescent part of the spectra was investigated. Commercial powders of Y2O3, purity better then 99.9 %, produced by three different suppliers were investigated. Raman spectra were recorded with computerized DILOR Z24 triple monochromator with Coherent Innova 100 argon ion laser, operating at 514.5 and 488 nm, which was used for the excitation. The milling was performed in air using Fritschs’ planetary ball mill. The milling time was varied from 1 min to 3 hours. The change of the excitation line helped to separate the luminescent from the Raman part of the spectrum. An extra investigation concerning sample humidity was undertaken. These results confirmed our doubt that the luminescent bands strongly depend on the ad(b)sorbed water. Their intensities notably increased after additional moisturizing with water vapor but decreased and almost disappeared after heating in air at 1100°C. Since water alone does not exhibit such luminescence spectrum, one should consider the mechanism of incorporation of water in the crystal lattice of Y2O3. Although the changes of crystal structure of Y2O3 from cubic to monoclinic structure during ball-milling in argon atmosphere was reported  1 , in our milling experiment performed in air such phase transition was not observed. On the other hand, the luminescent part of the Y2O3 spectrum vanished by milling. High energy transfer from balls to powder could explain the disappearance of the water, caused by local heating, and the absence of the luminescent effect.

Y2O3; Raman spectroscopy; luminiscence

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