Tb L 3 -edge X-ray Absorption Near-edge Structure Spectroscopic Analysis of Terbium-doped Phosphor Compoundsfor Plasma D
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Kee-Sun Sohna) Department of Materials Science and Metallurgical Engineering, Sunchon National Univeristy, Sunchon, Chonam 540-742, Republic of Korea
Kyong Hon Kim Telecommunication Basic Research Laboratory, Electronics and Telecommunications Research Institute, Taejon 305-600, Republic of Korea
Hee Dong Park Display Phosphor Group, Korea Research Institute of Chemical Technology, Taejon 305-600, Republic of Korea (Received 18 July 2001; accepted 9 October 2001)
We have analyzed Tb L3-edge x-ray absorption near-edge structure spectra of Tb-doped phosphor compounds for plasma display panel applications. Intensity and lifetime of the green emission from the Tb3+: 5D4 → 7F5 transition were measured with respect to nominal terbium concentration in the host compounds, i.e., YBO3, YPO4, and Y4Al2O9, all of which were made through the solid-state reaction. Typical concentration quenching was evident on the fluorescence intensity and the fluorescing level lifetime in our samples. From the analyses of white line absorption peaks at Tb L3-edge, it was verified that terbium is essentially trivalent in all the samples, even in very highly concentrated ones. Thus, this implies that the concentration quenching was not caused by presence of mixed-valent states of terbium. Instead, it is believed that a nonradiative energy transfer route among Tb3+ ions might be responsible for the behavior.
I. INTRODUCTION 3+
The green emission originated from the Tb : D4 → 7F5 transition in a dielectric medium is regarded to be useful for plasma display panel (PDP) applications. Yttrium-containing oxide compounds would be a good host of terbium doping in this case, and so far research efforts have been focused on these materials such as YBO3, YPO4, and Y4Al2O9.1–5 For the practical applications, a successful terbium-doped yttrium oxide phosphor should meet several conditions in view of green emission properties as follows. First, the excitation efficiency of green emission in vacuum ultraviolet wavelengths should be improved. Second, the color chromaticity as well as luminance should be also improved. Last and more important, the 10% decay time should exactly satisfy the requirement for plasma display panel (PDP). Even though several pros and at the same 5
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Address all correspondence to this author. e-mail: [email protected] J. Mater. Res., Vol. 17, No. 1, Jan 2002
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time a few cons concern the yttrium-containing compounds doped with terbium, these materials could be potential candidates for PDP applications.4 –7 So-called concentration quenching phenomena are quite well known in the green emission of Tb3+-doped dielectric materials, which arise in common regardless of the host materials used. Of course, not only the onset concentration where the concentration quenching becomes apparent but also the detailed quenching mechanisms differ more or less in every other host materials.4 –9 It is true, however, that the decrease of lifetime as well as emission intensity associated with
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