Photoluminescence properties of Tb3+ doped Al2O3 microfibers via a hydrothermal route followed by heat treatment

Uniform Al2O3:Tb3+ microfibers were synthesized via a hydrothermal route and thermal decomposition of a precursor of Tb3+ doped ammonium aluminum hydroxide carbonate, and characterized by X-ray diffraction (XRD), scanning electron microscope (SEM), photoluminescence (PL) spectra and decay curves. XRD results indicate that various crystallographic phase Al2O3:Tb3+ microfibers are obtained by postannealing at different temperatures. SEM results show that the length and diameter of these Tb3+ doped α-Al2O3 microfibers are about 6–8 μm and 300 nm, respectively. The PL spectra indicate that the 5D4 → 7F5 (545 nm) electric dipole transition is the most intensive when excited at 240 nm. It is shown that the 2.0 mol% of doping concentration of Tb3+ ions in α-Al2O3:Tb3+ is optimum. According to Dexter's theory, the critical distance between Tb3+ ions for energy transfer was determined to be 12.7 Å. It is found that the decay curves follow the single-exponential decay.