Luminescent Properties of Al2O3:Tb3+ Powders Embedded in Polyethylene Terephthalate Films

The luminescent properties of Al₂O₃:Tb³⁺ powders embedded in polyethylene therephtalate (PET) films have been studied. Luminescent Al₂O₃:Tb³⁺ polycrystalline powders were synthesized by a simple evaporation method. X-ray diffraction (XRD) spectrum of powders of Al₂O₃:Tb³⁺ have the α-Al₂O₃ crystalline phase with peaks located at 2Θ = 25.78, 35.34, 37.96, 43.56, 45.8, 52.74, 57.7, 61.5, 66.74, 68.44, 77.12 and 80.94, which are associated with the planes (012), (104), (110), (113), (202), (024), (116), (018), (214), (300), (119) and (220), and the δ-Al₂O₃ phase is also present as identified  by peaks in 2Θ = 32.82, 45.8, 61.36 and 66.74, associated with the planes (220), (400), (511) and (440). The powder embedded films were obtained by the spray pyrolysis technique. The photoluminescence and cathodoluminescence emission spectra from these samples show, in both cases, luminescence peaks associated with transitions within the electronic energy levels of Tb³⁺ ions. The dominant peak is at 544nm corresponding to the ⁵D₄→⁷F₅ transition and present ⁵D₄→⁷F_6, ⁵D₄→⁷F₄ y ⁵D₄→⁷F₃ transitions in 494, 587 y 622nm, when excited with λ_exc = 299 nm at room temperature. The CIE coordinates for non-doped PET films are (x = 0.2045,  y = 0.3636), when excited with 270nm, this emission falls in the blue region. CIE diagram for powder embedded PET films excited with 299 nm have coordinates (x = 0.31, y = 0.5111); in this case, the emission is a combination of Al₂O₃:Tb³⁺ green light and PET blue light emissions. UV-Vis % transmission measurements on these films show that they are transparent (~ 80 and 95 %T).