Fabrication and luminescence properties of Al2O3:Tb3+ microspheres via a microwave solvothermal route

Al 2 O 3 :Tb 3+ green phosphors were synthesized via a microwave solvothermal and thermal decomposition route, and characterized by X-ray diffraction (XRD), scanning electron microscope (SEM), photoluminescence (PL) spectra, and decay curves. XRD results indicate that Tb 3+ doped samples are γ-Al 2 O 3 after being calcined at 773 K. SEM results show that the particles of Al 2 O 3 :Tb 3+ are hierarchically nanostructured microspheres assembled from nanosheets. The PL spectra indicate that the 5 D 4 → 7 F 5 (545 nm) electric dipole transition is the most intensive when excited at 235 nm. It is shown that 0.7 mol% of doping concentration of Tb 3+ ions in γ-Al 2 O 3 :Tb 3+ is optimum. According to Dexter's theory, the critical distance between Tb 3+ ions for energy transfer was determined to be 18.4 A. It is found that the curve followed the single-exponential decay. The excellent chromaticity coordinates of Al 2 O 3 :Tb 3+ phosphors, as defined by the International Commission on Illumination (CIE), indicate that it is a good candidate for use in light display systems and optoelectronic devices.