The relationship between photoluminescence quenching concentrations and excitation wavelengths in (Gd,Y)BO3:Tb
Introduction
The emission intensity of many phosphors as a function of activator concentration initially increases with activator concentration and then decreases, going through a maximum at some concentrations. The decrease in emission intensity at a high activator concentration is referred to as the phenomenon of “concentration quenching” [1], [2] and this optimal activator concentration with the highest emission intensity is considered as “quenching concentration” of phosphors. A complete characterization of the luminescence quenching concentrations in inorganic phosphors is very important not only for technological design considerations but also for the basic understanding of the physical excitation processes involved. Over the last decades, the quenching behaviors in oxide systems had been widely investigated in the cathode-ray ultraviolet (CUV), X-ray ultraviolet (XUV) and ultraviolet (UV) excitation regions [1], [2], [3], [4], [5], [6]. However, the majority only reported the quenching characteristics at one excitation wavelength without systematic investigation in an excitation region [2], [3], [4], [5], [6], [7], [8], [9], [10]. As a result, a point commonly overlooked in quenching studies on phosphors is the relationship between quenching concentrations and excitation wavelengths. Moreover, the quenching behaviors in the vacuum ultraviolet (VUV) region are rarely investigated because of the lack of proper VUV light source.
On the other hand, the (Gd,Y)BO3:Tb with a high absorption edge and shorter decay time in vacuum ultraviolet (VUV) region is a potential inorganic green phosphor for application in plasma display panels (PDPs), Hg-free lamps and back lighting fields [11], [12], [13], [14]. Developing a model to research on quenching behaviors in (Gd,Y)BO3:Tb is significant to understand its photoluminescence properties, excitation pathways and quenching mechanisms, even developing some novel phosphors with efficient photoluminescence.
It is our fundamental aim to clarify the relationship between quenching concentrations and excitation wavelengths of typical (Gd,Y)BO3:Tb phosphors. In this work, the characteristics of quenching concentration in (Gd,Y)BO3:Tb under 130–290 nm were investigated completely and a possible quenching mechanism was proposed according to these results.
Section snippets
Experimental section
All (Gd,Y)BO3:Tb samples were prepared by solid-state method at 1100 °C for 3 h and were characterized as single phase by Rigaku D/max-2000 powder X-ray diffraction. Their photoluminescence was recorded on FLS-920T and ARC model VM-504 vacuum monochromator. The VUV excitation spectra were corrected by dividing the excitation intensity of sodium salicylate. All the spectra were recorded at room temperature.
Photoluminescence at 147 nm and 254 nm
The 147 nm and 254 nm are the most typical excitation sources for application in VUV and UV region, respectively. As for typical examples, Fig. 1 showed the emission spectra of typical Y0.94Tb0.06BO3 samples under 147 nm and 254 nm excitation. As shown in Fig. 1, the emission intensity of samples excited at 147 nm is much higher than that at 254 nm. The main emission peaks at about 476, 543, 570 and 621 nm are due to the 5D4–7F6, 5D4–7F5, 5D4–7F4 and 5D4–7F3 transitions of Tb3+, respectively
Conclusions
The photoluminescence quenching concentrations of (Gd,Y)BO3:Tb at particular excitation wavelengths are dependent on excitation bands in essence. The quenching concentrations of emissions due to electrostatic interaction are often small and those corresponding to exchange interaction are usually larger. In addition, the luminescence sensitization of Gd3+ and Y3+ ions would significantly influence the quenching behaviors. This dependence should be involved in the excitation mechanisms, types of
Acknowledgements
This work was supported by Program for New Century Excellent Talents in University of China (NCET, 04-0978) and Chinese Specialized Research Fund for the Doctoral Program of Higher Education (SRFDP, 20040730019).
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