Sensitization of Tb3+ luminescence with Ce3+ in LaOBr: Tb3+, Ce3+ |
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Authors: | Jorma Ho¨lsa¨ Markku Leskela¨ Lauri Niinisto¨ |
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Institution: | Department of Chemistry, Helsinki University of Technology, Otaniemi, SF-02150 Espoo 15, Finland |
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Abstract: | Luminescence emission and uv-excitation properties of LaOBr: Tb3+, LaOBr: Ce3+, and LaOBr: Tb3+, Ce3+ phosphors were studied. The visible emission spectra of La0.995Tb0.005OBr consists of5D3,4 →7F3–6 transitions in the wavelength range of 410–630 nm. The excitation of the Tb3+ ion gives a broad 4f → 5d transition band at 254 nm and weaker4f → 4f transition lines above 300 nm. The uv-excitation and emission of La0.995Ce0.005OBr at 290, 315, 355 (excitation), and 440 nm (emission) originate from transitions between the 4f-ground state and the four crystal field components of the5d2D excited state. The sensitization of Tb3+ luminescence in LaOBr with Ce3+ at varying concentrations is described and discussed. With increasing Ce3+ concentration the 5D3 →7F transitions of Tb3+ quench totally and the5D4 →7F transitions begin to quench gradually. The excitation spectrum of the5D4 →7F5 transition of Tb3+ consists of four bands due to Tb3+ and Ce3+, of which the three Ce3+ bands increase in intensity and the Tb3+ band decreases as the Ce3+ concentration is increased. |
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