Europium-doped fiber-like Al2O3 and its photoluminescence properties

Uniform Al2O3:Eu3+ microfibres were synthesized via a hydrothermal route and heat treatment (1173 K/2 h) of a precursor of Eu3+-doped ammonium aluminium hydroxide carbonate (NH4Al(OH)2CO3). The length and diameter of these Eu3+-doped Al2O3 microfibres are about 4–7 μm and 400 nm, respectively. Upon excitation at 394 nm, the orange-red emission bands were from 5D0 → 7FJ (J = 1, 2) transitions. The asymmetry ratio of (5D0 → 7F2)/(5D0 → 7F1) intensity is about 0.99, 1.43, 2.24, 2.40, 1.63 for the Eu3+ concentration 0.05, 0.30, 0.70, 0.90 and 1.20 mol-%, respectively. These values suggest that the asymmetry ratio of Eu3+ ions is related to the doping concentration. The maximum doping concentration of Eu3+ ions in Al2O3 is 0.9 mol-%. According to Dexter’s theory, the critical distance between Eu3+ ions for energy transfer was determined to be 17 A.