Naslov
Influence of microstructure to luminescence in Y2O3 powders

Autori
Gajović, Andreja ; Furić, Krešimir ; Tomašić, Nenad ; Su, Dangsheng ; Schloegl, Robert

Vrsta, podvrsta i kategorija rada
Sažeci sa skupova, sažetak, znanstveni

Izvornik
Proceedings, 7th Multinational Congress on Microscopy / Čeh, Miran ; Dražič, Goran ; Fidler, Sanja - Ljubljana : Slovene Society for Microscopy, Department for Nanostructured Materials - Jožef Štefan Institute, 2005, 165-166

Skup
7th Multinationl Congress on Microscopy

Mjesto i datum
Portorož, Slovenija, 26.06.2005. - 30.06.2005

Vrsta sudjelovanja
Predavanje

Vrsta recenzije
Međunarodna recenzija

Ključne riječi
luminescence; Y2O3; Raman spectroscopy; TEM

Sažetak
For decades yttrium oxide has been an important material in ceramic industry. It was used in the first synthesized ceramic superconductor, but nowadays plays an important role in preparation of novel light-emitting materials. Changes of Y2O3 luminescence band intensity as a consequence of different processes, such as moisturizing, heating and ball-milling, were observed in Raman spectra. In this work transmission electron microscopy (TEM) and selected area electron diffraction (SAED) were used to investigate changes in microstructure of Y2O3 at nanometric scale that influenced the luminescence properties. Commercial powders of Y2O3 (purity 99.99 %) were investigated. A high energy ball-milling was used for modifying the microstructure. The Raman spectra were recorded with a DILOR Z24 triple monochromator using the 514.5 and 488 nm laser lines for the excitation. TEM and SAED were performed in a Philips CM200 FEG operated at 200 kV. For X-ray diffraction patterns (XRD) a Philips PW 3040/60 X'pert Pro powder diffractometer was used with Cu Kα 1 radiation. An investigation concerning sample humidity confirmed 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 at 1100°C in vacuum. The changes of crystal structure of Y2O3 due to moisturizing or heating were not observed by XRD. Since water alone does not exhibit such luminescence spectrum, one should consider the mechanism of incorporation of water (or OH‾ ) in the crystal lattice of Y2O3. With increasing ball-milling time the luminescent band in Y2O3 Raman spectra decreased and finally vanished after 1 h milling (Fig. 1a). This change in Raman spectra was accompanied by the changes of crystal structure from cubic to monoclinic (Fig. 1b). However, the luminescence of monoclinic Y2O3 has been reported in literature (1). High energy transfer from balls to powder could explain the expulsion of water (or OH‾ ) causing the disappearance of the luminescent effect, but the luminescence was lacking in milled samples even after long time spent in normal atmosphere. The particle sizes decreased through milling (Fig. 2a and 2c) as it was more significantly shown in Fig. 2b and 2d. The absent of luminescence in nanometric-sized crystallites could not be explained in terms of surface adsorbed OH‾ and CO3‾ (2) as it was also confirmed by humidity experiments. The absent of the luminescence in Y2O3 nano-powders could be attributed to an increase of grain boundaries that influenced the mechanism of relaxation processes after excitation by 514.5 nm laser line. REFERENCES: (1) D. K. Williams, B. Bihari, B. M. Tissue and J. M. McHale, J. Phys. Chem. B 102 (1998), 916. (2) F. Vetrone, J.-C. Boyer, J. A. Capobianco, A.Speghini, M. Bettineli, Chem. Mater. 15 (2003) 2737.

Izvorni jezik
Engleski

Znanstvena područja
Fizika, Geologija

POVEZANOST RADA