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Acetylacetone has been used as a chemical modifier for the synthesis of undoped and Tb3+-doped Y3Al5O12powders. A systematic investigation concerning its influence on the structural and morphological properties of amorphous and crystallized samples has been carried out. These properties have been comparatively studied by means of X-ray diffraction, infrared spectroscopy, SEM, XAS and SAXS. 27Al NMR and EPR experiments have been performed to complete the study. The combined results have evidenced that acetylacetone promotes organic groups departure during calcination, entailing a better structural organization at lower temperatures compared with unmodified powders. Structuration has been proven to occur at short-scale range until a 600 °C heating treatment before being extended by coalescence at higher temperatures. Finally, the presence of acac ligands on the alkoxides leads to a monomer-cluster aggregation process, and thus to a more open network. [ABSTRACT FROM AUTHOR]

Tb3+-doped Y3Al5O12powders have been synthesized from alkoxide precursors using, or not using, acetylacetone as a chemical modifier. The terbium oxidation state and local environment of amorphous and crystallized powders have been comparatively investigated by means of X-ray absorption near-edge structures (XANES) and extended X-ray absorption fine structure (EXAFS) while laser-induced luminescence was used to study their optical properties. Excitation and emission spectra have been recorded and a relative luminescence yield has been assessed upon 277 nm excitation. Whatever the sample, the terbium oxidation state remains +III and, for a similar heating treatment until 900 °C, its local environment appears to be better organized in powders modified by acetylacetone. Structural parameters obtained during XAS study are consistent with the YAG structure in which Tb atoms are in solid solution with Y ones. Besides, Tb3+characteristic green luminescence has been recorded for all samples, even those amorphous. It has been evidenced that the use of acetylacetone leads to more efficient luminescent materials for calcination temperatures ranging from 400 °C to 900 °C upon 277 nm excitation. Discrepancies between optical properties will be discussed with regards to the terbium local environment and expected luminescence features. [ABSTRACT FROM AUTHOR]