Structural and Optical Properties of Highly Nd‐Doped Yttrium Aluminum Garnet Ceramics from Alkoxide and Glycolate Precursors

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 Nd 3+ 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 Nd 2 O 3 phase (X‐ray diffraction) during sintering. High‐resolution absorption spectra ( 4 I 9/2 (1)→ 4 F 9/2 (1)) of the powders showed that a higher absorption cross‐section of glycolate‐derived powders is due to Nd 3+ –Nd 3+ 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.