Luminescence and decay behaviors of Tb-doped yttrium silicate
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Kee-Sun Sohna) and Hee Dong Park Display phosphor Group, Korea Research Institute of Chemical Technology, Taejon 305-600, Korea
Se Young Choi Yonsei University, Seoul 120-749, Korea (Received 10 October 2000; accepted 5 January 2001)
The photoluminescence of terbium-activated yttrium silicate with the general formula Y2−XTbxSiO5 was investigated as a function of Tb3+ concentration. Especially, the main attention was focused on the 5D3 fluorescence and its energy transfer behavior. The emission and excitation spectra were measured in terms of Tb3+ concentration. The diffuse reflectance spectrum was also measured in the range from VUV to UV. As a result, yttrium silicate was found to have a broad absorption band extended from the VUV to UV range. The concentration quenching was investigated in terms of luminance and decay time both for 5D3 and 5D4 fluorescence. The energy transfer was also investigated by analyzing the decay curve of 5D3 emission on the basis of the multipolar interaction. The decay curves of 5D3 emission, for which well-known cross-relaxation has been accepted as a main factor, were analyzed by Inokuti and Hirayama’s formula on the basis of the direct quenching scheme. Furthermore, the rate equations including a newly proposed quenching scheme were taken into consideration. The rate equations accept the emission quenching as due to the cross-relaxation from 5D3 or 4 to some upper levels such as 7D and the charge-transfer band.
I. INTRODUCTION
The PL property of many phosphors has been studied widely for last few years as there has been a growing interest in plasma display panels (PDP). Especially, the green component of the three color centers is the most important part by considering susceptibility of human eye and the green portion of constituent pixels, which is 3:6:1 (red:green:blue).1 Most studies of the green component have been focused on Mn-activated phosphor or YAG:Tb. The present investigation aims at elucidating PL properties of Y2SiO5:Tb on the basis of the possibility that this phosphor could be applied for the green component of PDP. Generally, the energy level structure of Tb-activated phosphors is well known. The cross relaxation, which is the energy transfer from 5D3 to 5D4,2 is also a wellknown phenomenon. The cross relaxation becomes prominent at increasing Tb3+ concentration. As a matter of fact, there have been a lot of investigations dealing with PL behaviors of YAG:Tb. 3–10 In particular,
a)
Address all correspondence to this author. J. Mater. Res., Vol. 16, No. 3, Mar 2001
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YAG:Tb has been investigated extensively for its potential as a phosphor for projection TV.5–10 However, the detailed investigation on PL and decay property of Y2SiO5:Tb could be scarcely found. So it is necessary to investigate the PL and decay properties of this phosphor in association with the proper energy transfer scheme. We confirmed that Y2SiO5:Tb exhibits similar behaviors to other Tb-activated phosphors, but there is a slight difference
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