Yttrium aluminum garnet (YAG) nanopowders doped with high neodymium (Nd) content (3 at.%) were synthesized by the sol–gel processing of (i) alkoxide precursors and (ii) metal chelates formed by complexing the cations with polyethylene glycol. A stoichiometric YAG composition was obtained following both procedures; however, the agglomeration of particles was significantly higher in glycolate synthesis, which shielded residual organics from oxidation (elemental analyses).
Distribution of Nd3+ ions in the YAG matrix, as shown by the absorption of pump energy and photoluminescence spectra of Nd:YAG ceramics, was more homogeneous in alkoxide-derived powders. The segregation of Nd centers in the glycolate-derived sample was supported by the precipitation of a crystalline Nd2O3 phase (X-ray diffraction) during sintering.
High-resolution absorption spectra (4I9/2(1)→4F9/2(1)) of the powders showed that a higher absorption cross-section of glycolate-derived powders is due to Nd3+–Nd3+ ion pairing, which leads to the quenching of photoluminescence. Owing to the better dispersion of optically active centers, the photoluminescence signal was found to be substantially enhanced in alkoxide-derived Nd:YAG ceramics.
Mathur, S., Shen, H., Veith, M., Rapalaviciute, R. and Agne, T., 2006. Structural and Optical Properties of Highly Nd‐Doped Yttrium Aluminum Garnet Ceramics from Alkoxide and Glycolate Precursors. Journal of the American Ceramic Society, 89(6), pp.2027-2033.
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