[17a-K310-1~9] 15.1 バルク結晶成長

11:45 〜 12:00奨励賞エントリー英語発表

[17a-K310-9] High Performance Y_1-xTb_xTaO₄ Single-Crystal Scintillators for X-ray Detection

〇(D)YUESHEN ZHOU^1,2, Dongsheng Yuan¹, Encarnacion G.Villora¹, Daisuke Nakauchi³, Takumi Kato³, Noriaki Kawaguchi³, Takayuki Yanagida³, Kiyoshi Shimamura^1,2 (1.NIMS, 2.Waseda Univ., 3.NAIST)

キーワード：

Scintillator、Single-crystal、Tantalates

In pursuit of a single-crystal scintillator that is free from toxic elements and has scintillation properties comparable to commercial CdWO₄ (CWO) in terms of light yield, afterglow, and stopping power, transparent and colorless Y_1−xTb_xTaO₄ (YTTO) mixed single crystals are grown by the floating-zone (FZ) technique and investigated for the first time as scintillators. In a previous study, we demonstrate that short sections (~4 mm in length) of transparent YTaO₄ (YTO) single crystals can be obtained using the FZ technique, despite the occurrence of phase transition. In the current study, we find that the length of the transparent region increases with the incorporation of Tb. For 10% Tb doping, the transparent region extends to approximately 10 mm; for 25% Tb, it further increases to about 20 mm. Upon complete substitution of Y by Tb, a monoclinic TbTaO₄ (TTO) transparent single crystal is grown for the first time, as shown in the photographs in Fig. 1(a). With the substitution of Y³⁺ by Tb³⁺, the intrinsic UV photoluminescence from YTO, stemming from the Ta−O complex, gradually decreases until only the intraionic Tb³⁺ emissions remain for a Tb concentration below 5%. The optimum scintillation performance is found for 15% Tb concentration: the light yield is ∼1.5 times that of CWO, as shown in Fig. 2(b), while the density, the stopping power, and the afterglow are comparable. For concentrations above 15% Tb³⁺, the quadrupole−quadrupole interaction is found to be responsible for the concentration quenching. These results demonstrate the potential of Y_0.85Tb_0.15TaO₄ single crystals as an environmentally friendly alternative to CWO ones for high-energy X-ray radiography.