Elaboration and characterization of transparent GdTaO4:Tb3+ thick films fabricated by sol-gel process

Transparent GdTaO4:Tb3+ polycrystalline thick films have been successfully synthesized using sol-gel technique. The critical thickness of the film was 760 nm and the surface was crack-free and smooth. The thick film particle size was 25 nm and the powder particle size was over micron. In comparison with the thick film phosphors, the charge transfer transition of TaO4 group and the excitation peak of Tb3+ center shifted from 223 to 215 nm and 245 to 255 nm for powder sample, respectively. The higher energy level of the charge transfer indicated the decrease of the covalency of the Ta-O bond in the powder phosphor. The red shift of the 4f-5d excitation band might be attributed to the quantum confinement of Tb3+ in the film phosphor. The decay times of GdTaO4:Tb3+ thick film and powder phosphors were 0.79 and 1.02 ms, respectively.