Atomic position and the chemical state of an active Sn dopant for Sn-doped -GaO(001)

Tsai, Y. H.*; Kobata, Masaaki; Fukuda, Tatsuo; Tanida, Hajime; Kobayashi, Toru; Yamashita, Yoshiyuki*

Applied Physics Letters, 124(11), p.112105_1 - 112105_5, 2024/03

https://doi.org/10.1063/5.0198160

The Damage analysis for irradiation tolerant spin-driven thermoelectric device based on single-crystalline YFeO/Pt heterostructures

Ieda, Junichi; Okayasu, Satoru; Harii, Kazuya*; Kobata, Masaaki; Yoshii, Kenji; Fukuda, Tatsuo; Ishida, Masahiko*; Saito, Eiji

IEEE Transactions on Magnetics, 58(8), p.1301106_1 - 1301106_6, 2022/08

https://doi.org/10.1109/TMAG.2022.3145888

The combination of spin-driven thermoelectric (STE) devices based on spin Seebeck effect (SSE), and radioactive isotopes as heat sources, has potential as a next-generation method of power generation in applications such as power supplies for space probes. However, there has been very limited knowledge available indicating the irradiation tolerance of spin thermoelectric devices. Through analysis using a heavy ion-beam accelerator and the hard X-ray photoemission spectroscopy (HAXPES) measurements, we show that a prototypical STE device based on YFeO/Pt heterostructures has tolerance to irradiation of high-energy heavy-ion beams. We used 320 MeV gold ion beams modeling cumulative damages due to fission products emitted from the surface of spent nuclear fuels. By varying the dose level, we confirmed that the thermoelectric and magnetic properties of the SSE elements are not affected by the ion-irradiation dose up to ions/cm fluence and that the SSE signal is extinguished around ions/cm, in which the ion tracks almost fully cover the sample surface. In addition, the HAXPES measurements were performed to understand the effects at the interface of YFeO/Pt. The HAXPES measurements suggest that the chemical reaction that diminishes the SSE signals is enhanced with the increase of the irradiation dose. We share the current understandings of the damage analysis in YFeO/Pt for developing better STE devices applicable to harsh environmental usages.

High temperature reaction of multiple eutectic-component system; The Case of solid metallic Zr and molten stainless steel-BC

Sumita, Takehiro; Kobata, Masaaki; Takano, Masahide; Ikeda, Atsushi

Materialia, 20, p.101197_1 - 101197_11, 2021/12

https://doi.org/10.1016/j.mtla.2021.101197

Tolerance of spin-Seebeck thermoelectricity against irradiation by swift heavy ions

Okayasu, Satoru; Harii, Kazuya*; Kobata, Masaaki; Yoshii, Kenji; Fukuda, Tatsuo; Ishida, Masahiko*; Ieda, Junichi; Saito, Eiji

Journal of Applied Physics, 128(8), p.083902_1 - 083902_7, 2020/08

AA2020-0071.pdf:0.69MB

https://doi.org/10.1063/5.0014229

Hard X-ray photoelectron spectroscopy study of Pt/YFeO

Kobata, Masaaki; Yoshii, Kenji; Fukuda, Tatsuo; Kawasaki, Ikuto; Okane, Tetsuo; Yamagami, Hiroshi; Yaita, Tsuyoshi; Harii, Kazuya; Ieda, Junichi; Okayasu, Satoru; et al.

JPS Conference Proceedings (Internet), 30, p.011192_1 - 011192_6, 2020/03

https://doi.org/10.7566/JPSCP.30.011192

High energy X-ray photoelectron spectroscopy (HAXPES) measurements were carried out for the Spin Seebeck system Pt/YFeO(YIG). This system was found to show anomalous Hall effect, possible due to the formation of intermetallic compounds between Fe and Pt. To reveal this possibility, we have measured the Fe 1s photoelectron peaks by using HAXPES. It was found that the Fe ions consist of Fe in YIG and metallic Fe. The formation of the metallic state is consistent with the proposed origin of the anomalous Hall effect. Other spectra such as Pt 4f will be presented at the conference.

Current status and future developments of hard X-ray photoelectron spectroscopy

Kobata, Masaaki; Okane, Tetsuo; Kobayashi, Keisuke*

Bunko Kenkyu, 67(4), p.161 - 162, 2018/08

We introduce hard X-ray photoelectron spectroscopy, which has been rapidly introduced and developed in synchrotron radiation facilities. In particular, in order to realize electronic state analysis by hard X-ray photoelectron spectroscopy of insulators, the developed charge neutralization method was described. As an example, we showed adsorption behavior of cesium to nuclear reactor structure assuming Fukushima Daiichi Nuclear Power Plant accident. Finally, future prospects of hard X-ray photoelectron spectroscopy will be described.

Electronic structure of ThRuSi studied by angle-resolved photoelectron spectroscopy; Elucidating the contribution of U 5 states in URuSi

Fujimori, Shinichi; Kobata, Masaaki; Takeda, Yukiharu; Okane, Tetsuo; Saito, Yuji; Fujimori, Atsushi; Yamagami, Hiroshi; Matsumoto, Yuji*; Yamamoto, Etsuji; Tateiwa, Naoyuki; et al.

Physical Review B, 96(12), p.125117_1 - 125117_9, 2017/09

https://doi.org/10.1103/PhysRevB.96.125117

Results and progress of fundamental research on FP chemistry

Osaka, Masahiko; Nakajima, Kunihisa; Miwa, Shuhei; Di Lemma, F. G.*; Miyahara, Naoya; Suzuki, Chikashi; Suzuki, Eriko; Okane, Tetsuo; Kobata, Masaaki

Proceedings of 8th European Review Meeting on Severe Accident Research (ERMSAR 2017) (Internet), 11 Pages, 2017/05

Fundamental research on fission product (FP) chemistry is underway at Japan Atomic Energy Agency. The purpose is to establish a FP chemistry database in each region of a LWR under severe accident conditions. Improvement of FP chemical models based on this database is also an important task of the research. Research outputs are reflected to the research and development of decommissioning of Fukushima Daiichi Nuclear Power Station (1F) and the enhancement of LWR safety. Four research items have thus been established considering the specific issues of 1F and the priority in the source term research area, as follows: - Effects of boron (B) release kinetics and thermal-hydraulic conditions on FP behavior, - Cesium (Cs) chemisorption and reactions with structural materials, - Establishment of a thermodynamic and thermophysical properties database for FP compounds, - Development of experimental and analytical techniques for the reproduction of FP behavior. In this paper, results and progress of the research are presented.

Results and progress of fundamental research on fission product chemistry; Progress report in 2015

Osaka, Masahiko; Miwa, Shuhei; Nakajima, Kunihisa; Di Lemma, F. G.*; Suzuki, Chikashi; Miyahara, Naoya; Kobata, Masaaki; Okane, Tetsuo; Suzuki, Eriko

JAEA-Review 2016-026, 32 Pages, 2016/12

JAEA-Review-2016-026.pdf:6.18MB

A fundamental research program on fission product (FP) chemistry has started since 2012 for the purpose of establishment of a FP chemistry database in each region of LWR under severe accident and improvement of FP chemical models based on the database. Research outputs are reflected as fundamental knowledge to both the research and development of decommissioning of Fukushima Daiichi Nuclear Power Station (1F) and enhancement of LWR safety. Four research items have thus been established considering the specific issues of 1F and the priority in the source term research area, as follows: effects of boron (B) release kinetics and thermal-hydraulic conditions on FP behavior, cesium (Cs) chemisorption and reactions with structural materials, enlargement of a thermodynamic and thermophysical properties database for FP compounds and development of experimental and analytical techniques for the reproduction of FP behavior and for direct measurement methods of chemical form of FP compounds. In this report, the research results and progress for the year 2015 are described. The main accomplishment was the installation of a reproductive test facility for FP release and transport behavior. Moreover, basic knowledge about the Cs chemisorption behavior was also obtained. In addition to the four research items, a further research item is being considered for deeper interpretation of FP behavior by the analysis of samples outside of the 1F units.

Hard X-ray photoelectron spectroscopy study for transport behavior of CsI in heating test simulating a BWR severe accident condition; Chemical effects of boron vapors

Okane, Tetsuo; Kobata, Masaaki; Sato, Isamu*; Kobayashi, Keisuke*; Osaka, Masahiko; Yamagami, Hiroshi

Nuclear Engineering and Design, 297, p.251 - 256, 2016/02

https://doi.org/10.1016/j.nucengdes.2015.10.029