Yellow-light emitting Tb3Al5O12:Ce3+ phosphor properties sensitized by Bi3+ ions

A new yellow-light emitting garnet phosphor Tb3Al5O12:Ce3+, Bi3+ (TAG:Ce3+, Bi3+) was synthesized by the metal organic decomposition method. The phosphor properties with different Ce3+/Bi3+ dopant concentrations were studied in detail using X-ray diffraction (XRD) analysis, photoluminescence (PL) and PL excitation spectroscopies, and diffuse reflectance measurements. The optimum concentrations of Ce3+ /Bi3+ deduced from the PL intensity measurements by excitation at lambda(ex) = 325 nm were similar to 0.2 mol% (Ce3+ and Bi3+). The addition of Bi3+ ions into the Ce3+ singly doped phosphor increased similar to 43% of the PL intensity. The XRD data further suggested an improvement in the crystalline quality of the Ce3+ singly doped phosphor by codoping with Bi3+. An increase in the PL intensity was attributed to an energy transfer from Tb3+ to Bi3+ and Ce3+ together with an improved crystalline quality of the (Ce3+, Bi3+)-codoped phosphor. Temperature dependence of the luminescence intensities was also measured at T = 20-500 K in 10-K increments and analyzed using the conventional model with thermal quenching energies of E-q1 = 35 meV and E-q2 = 0.40 eV. The experimental data for the Ce3+ singly doped phosphor, however, required an additional term of trap states with energy of E-t = 3 meV, in agreement with poor crystalline quality of the TAG:Ce3+ phosphor.