[20p-D62-1~14] 15.1 バルク結晶成長

16:00 〜 16:15奨励賞エントリー英語発表

[20p-D62-12] Y(Ta_1-xNb_x)O₄ single-crystal scintillators

〇(D)YUESHEN ZHOU^1,2, Dongsheng Yuan¹, Garica Villora¹, Kiyoshi Shimamura^1,2 (1.NIMS, 2.Waseda Univ.)

キーワード：

Tantalates、Single-crystal、Scintillator

Environmental-friendly alternatives to the commercial scintillator CdWO₄, which contains the toxic element Cd, are highly desired. As potential candidates, in this work the scintillation characteristics of single-crystals of the rare-earth tantalate family Y(Ta_1-xNb_x)O₄ are studied. Bulk single-crystals of the Fergusonite structure are grown by the floating-zone (FZ) method covering the whole solid-solution range from YTaO₄ to YNbO₄. Figure 1(a) shows the stable melt growth of crystals by the FZ. Due to phase transitions upon cooling, transparent single-crystal areas are obtained only partially, as the one seen in the inset. Both YTaO₄ and YNbO₄ exhibit a unique broad X-ray luminescence centered at 339 and 407 nm, respectively. Mixed crystals (up to 2% Nb partial substitution) exhibit both emissions with different ratios depending on composition. The X-ray luminescence spectra are shown in Fig. 1(b). The highest radioluminescence (15900 ph/MeV) and the lowest afterglow (0.008% @ 40 ms) are found for the YTaO₄ crystal. These two characteristics are comparable to those of CdWO₄. However, the emission shift from UV to visible by Nb-substitution is preferable for Si-photodiode detection, as in the case of CdWO₄. The optimum Nb concentration for maximum X-ray detection performance is discussed considering the absorption cross-sections, and the emission and detector efficiencies.