Influence of a chelating agent on optical and morphological properties of YAG: Tb3+ phosphors prepared by the sol-gel process

Chemical modifications are widely used in sol-gel method in order to control the mechanisms involved during hydrolysis-condensation and polymerization processes. In this paper, the influence of acetylaceton (acac) used as a chelating agent in the synthesis of undoped and Tb³⁺-doped Y₃Al₅O₁₂ (YAG) powders and sols, has been investigated. Its effects on samples crystallization and morphology have been studied by means of high-temperature X-ray diffraction (HTXRD), thermal analysis (DTA-TG), infrared (IR) and Raman spectroscopies, transmission electron microscopy (TEM) and laser granulometry. It was shown that acetylaceton enhances the structural organization of YAG compound. Moreover, acac-modified powders exhibit much smaller particles than unmodified ones. Optical study has also been achieved on doped samples. Laser induced luminescence spectra and fluorescence decays of Tb³⁺ ions show that acac affects the optical properties of YAG: Tb³⁺ for any types of samples (sol, xerogel or crystallized powder). Powders demonstrate a better luminescence yield without acetylaceton, whereas stabilized sols are more efficient than unstabilized ones.