Speaker
Description
Shunsuke Kurosawa$^{1,2*}$, Koichi Harata$^3$, Shohei Kodama$^3$, Shinosuke Yamato$^3$, Akihiro Yamaji$^3$, Jan Pejchal$^4$, Yuji Ohashi$^3$, Kei Kamada$^{1, 5}$, Yuui Yokota$^{1}$, Akira Yoshikawa$^{1, 3, 5}$
$^1$New Industry Creation Hatchery Center (NICHe)
6-6-10 Aoba, Aramaki, Aoba-ku, Sendai, Miyagi 980-8579, Japan
$^2$Faculty of Science, Yamagata University, Kojirakawa-machi 1-4-12, Yamagata 990-8560, Japan
$^3$Institute for Materials Research (IMR), Tohoku University
2-1-1 Katahira,Aoba-ku,Sendai,Miyagi 980-8577, Japan
$^4$Institute of Physics, AS CR, Cukrovarnická 10, 162 53 Prague, Czech Republic.
$^5$ C&A Corporation, 6-6-40 Aoba, Aramaki, Aoba-ku, Sendai, Miyagi 980-8577, Japan.
Scintillators are used in medical imaging and high-energy physics as radiation detectors, and high effective atomic number materials are required in order to obtain the high gamma-ray detection efficiency. Recently, pyrochlore structure type materials have been investigated as scintillation materials, because these materials had good light outputs [1]. Since La$_{2}$Hf$_{2}$O$_{7}$, a member of the pyrochlore group, has high an effective atomic number of approximately 62, this material can be high gamma-ray detection efficiency. On the other hand, the melting point of this material is over 2,500 $^\circ$C. Since almost crucibles cannot be operated under the such high temperature, and the common single-crystal-growth method is hard to apply to this material. Thus, we investigate the luminescent properties of La$_{2}$Hf$_{2}$O$_{7}$ as ceramics. Here, the spark plasma sintering (SPS) method is one of the methods to fabricate the ceramics, and it takes shorter time to obtain the ceramics compared with other methods such as HIP.
First, pure RE-doped La$_{2}$Hf$_{2}$O$_{7}$ ceramics powers were prepared by the solid state reaction, where is Eu, Tb, and transparent ceramics were obtained by the SPS method. All samples were confirmed to be the single phase, and these samples had transparency.
Both Eu and Tb-doped La$_{2}$Hf$_{2}$O$_{7}$ samples had some sharp emission peaks around 550-700 and 350-650 nm, respectively, in the radio luminescence spectra excited by X-rays or 5.5 MeV alpha rays from an $^{241}$Am source. Each peak was originated from Eu$^{3+}$ and Tb$^{3+}$ 4f-4f transition. In this paper, we show the optical and scintillation properties of these materials including temperature dependence and time profile in this presentation.
[1] A. Suzuki, S. Kruosawa, A. Yoshikawa et al., Applied Physics Express 5 102601(2012)
