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Synthesis by sol-gel method of nanocrystalline compounds within Y2O3(Nd2O3)–Al2O3 system for optical applications
|Ludwika Lipińska 1, Agnieszka Rzepka 1, Detlef Klimm 2, Witold Ryba-Romanowski 3, Anna Pajaczkowska 1|
1. Institute of Electronic Materials Technology (ITME), Warszawa 01919, Poland
In the Y2O3(Nd2O3)─Al2O3 system there are some compounds, very useful for optical applications. These are as follows: Y3Al5O12 (YAG), YAlO3 (YAP) and Y4Al2O9 (YAM). Also, Y2O3 (YO) doped by rare earth cations exhibits luminescent properties. All the above mentioned oxides in the form of nanocrystalline powders may be applied as stable phosphors or materials for laser ceramics. In this work, we have succeeded in preparing of YAG, YAG substituted by Nd, YAM and YO by the modified sol-gel method from aluminum nitrate, rare earth oxides and complexing compounds. All the substrates were carefully solved in acetic acid solutions and then - after the solvent’s removing – thermally treated. The obtained nanopowders had crystalline structure confirmed by X-ray diffraction (XRD). The size and morphology of nanopowders were analyzed by scanning electron microscopy (SEM). The mean size of crystallites was evaluated using Scherrer formula and the sizes increased with the calcining temperature from 10 to 75 nm. It’s worth mentioning that YAG can be doped by neodymium up to 27,5% without destroying the garnet’s structure. This value is considered to be the highest known level of yttrium substitution by neodymium in YAG. Highly doped powders (15, 25, 27,5 % Nd) were examined by thermal analysis of DTA . Luminescence spectra of YAG:Nd powders were recorded using Dongwoo Optron Fluometrer system. To conclude, the increase of Nd3+ concentration in YAG over 10 at. % causes very strong self-quenching of the Nd emission. Unexpectedly, the lifetime for the powder YAG sample containing 1% of Nd3+ is longer than the reported lifetimes for a YAG monocrystal samples. The yttrium oxides doped by neodymium and ytterbium ions were one-phase and of nanocrystalline structures. Spectroscopic examination of these nanopowders revealed occurrence of intense emission in near infrared region.
This work was supported by the Ministry of Education and Science under the research project No. 3T11B00430.
Presentation: Invited at E-MRS Fall Meeting 2007, Symposium A, by Ludwika Lipińska
See On-line Journal of E-MRS Fall Meeting 2007
Submitted: 2007-02-19 14:17 Revised: 2009-06-07 00:44