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Journal Articles

Structural behaviors of lead zirconate titanate-based ferroelectric ceramics during pyroelectric-power generation cycles

Kawasaki, Takuro; Fukuda, Tatsuo; Yamanaka, Satoru*; Murayama, Ichiro*; Kato, Takanori*; Baba, Masaaki*; Hashimoto, Hideki*; Harjo, S.; Aizawa, Kazuya; Tanaka, Hirohisa*; et al.

Journal of Applied Physics, 137(9), p.094101_1 - 094101_7, 2025/03

 Times Cited Count:0 Percentile:0.00(Physics, Applied)

Journal Articles

Synthesis of carbon nanowalls using plasma-irradiated solid carbon and absorption of Cs in water

Fukada, Yukimasa; Aoyagi, Yumito*; Yokoyama, Misaki*; Horibe, Yoichi*; Kano, Jun*; Kaneda, Miyu*; Fujii, Tatsuo*; Yoshigoe, Akitaka; Kobata, Masaaki; Fukuda, Tatsuo; et al.

Journal of Electronic Materials, 54, p.686 - 692, 2025/01

 Times Cited Count:0 Percentile:0.00(Engineering, Electrical & Electronic)

no abstracts in English

Journal Articles

Towards innovation to transform radioactive waste into resources; A Way of converting heat and radiation into electricity

Ieda, Junichi; Fukada, Yukimasa; Fukuda, Tatsuo

Nihon Genshiryoku Gakkai-Shi ATOMO$$Sigma$$, 66(10), p.521 - 524, 2024/10

no abstracts in English

Journal Articles

Fukushima Daiichi Nuclear Power Plant Accident; Understanding Formation Mechanism of Radioactive Particles through Sr and Pu Quantities

Igarashi, Junya*; Ninomiya, Kazuhiko*; Zheng, J.*; Zhang, Z. J.*; Fukuda, Miho*; Aono, Tatsuo*; Minowa, Haruka*; Yoshikawa, Hideki*; Sueki, Keisuke*; Satou, Yukihiko; et al.

Environmental Science & Technology, 58(33), p.14823 - 14830, 2024/08

 Times Cited Count:0 Percentile:0.00(Engineering, Environmental)

Journal Articles

SRPES and XPS analysis of activation and deterioration processes for Ti-Zr-V NEG coating

Kamiya, Junichiro; Abe, Kazuhide; Fujimori, Shinichi; Fukuda, Tatsuo; Kobata, Masaaki; Morohashi, Yuko; Tsuda, Yasutaka; Yamada, Ippei; Yoshigoe, Akitaka

e-Journal of Surface Science and Nanotechnology (Internet), 22(4), p.316 - 326, 2024/08

The activation and deterioration mechanisms of the Ti-Zr-V non-evaporable getter (NEG) coating have been investigated. Operando analysis of the surface chemical composition change of the Ti-Zr-V coating was performed by the synchrotron radiation photoelectron spectroscopy (SRPES) during the process of raising the sample temperature to 250$$^{circ}$$C, corresponding to the activation process of NEG coating. The surface oxidation process was also characterized by the SRPES during the injection of O_2 gas into the chamber while keeping the sample temperature at 250$$^{circ}$$C, corresponding to the deterioration process of NEG coating, i.e. surface oxidation and oxygen diffusion to the coating interior. The depth profile of the oxidized sample was measured with X-ray photoelectron spectroscopy. The results shows, in the activation process, the surface Zr gets the oxygen from the oxides of Ti and V at the first stage, resulting in the metallic Ti and V on the surface, and the oxygen of the Zr-oxide and/or Zr sub-oxides diffuse to the interior of the coating in the continuous temperature rise, resulting in the metallic Zr on the surface. It is further suggested that the deterioration of the Ti-Zr-V NEG coating means the Zr and secondary Ti are oxidized deep into the coating, resulting in the restriction of the oxygen migration from the NEG compositions on the surface and consequently the lack of surface metallization.

Journal Articles

Atomic position and the chemical state of an active Sn dopant for Sn-doped $$beta$$-Ga$$_{2}$$O$$_{3}$$(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

 Times Cited Count:2 Percentile:46.22(Physics, Applied)

Journal Articles

Direct energy conversion using Ni/SiC Schottky junction in $$^{237}$$Np and $$^{241}$$Am gamma ray regions

Fukuda, Tatsuo; Kobata, Masaaki; Shobu, Takahisa; Yoshii, Kenji; Kamiya, Junichiro; Iwamoto, Yosuke; Makino, Takahiro*; Yamazaki, Yuichi*; Oshima, Takeshi*; Shirai, Yasuhiro*; et al.

Journal of Applied Physics, 132(24), p.245102_1 - 245102_8, 2022/12

 Times Cited Count:1 Percentile:7.68(Physics, Applied)

Direct energy conversion has been investigated using Ni/SiC Schottky junctions with the irradiation of monochromatized synchrotron X-rays simulating the gamma rays of $$^{237}$$Np (30 keV) and $$^{241}$$Am (60 keV). From current-voltage measurements, electrical energies were obtained for both kinds of gamma rays. The energy conversion efficiencies were found to reach up to $$sim$$1.6%, which is comparable to those of a few other semiconducting systems reported thus far. This result shows a possibility of energy recovery from nuclear wastes using the present system, judging from the radiation tolerant nature of SiC. Also, we found different conversion efficiencies between the two samples. This could be understandable from hard X-ray photoelectron spectroscopy and secondary ion mass spectroscopy measurements, suggesting the formation of Ni-Si compounds at the interface in the sample with a poor performance. Hence, such combined measurements are useful to provide information that cannot be obtained by electrical measurements alone.

Journal Articles

The Damage analysis for irradiation tolerant spin-driven thermoelectric device based on single-crystalline Y$$_3$$Fe$$_5$$O$$_{12}$$/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

BB2021-0945.pdf:1.19MB

 Times Cited Count:1 Percentile:10.33(Engineering, Electrical & Electronic)

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 Y$$_3$$Fe$$_5$$O$$_{12}$$/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 $$10^{10}$$ ions/cm$$^2$$ fluence and that the SSE signal is extinguished around $$10^{12}$$ ions/cm$$^2$$, 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 Y$$_3$$Fe$$_5$$O$$_{12}$$/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 Y$$_3$$Fe$$_5$$O$$_{12}$$/Pt for developing better STE devices applicable to harsh environmental usages.

Journal Articles

${it Operando}$ structure observation of pyroelectric ceramics during power generation cycle

Kawasaki, Takuro; Fukuda, Tatsuo; Yamanaka, Satoru*; Sakamoto, Tomokazu*; Murayama, Ichiro*; Kato, Takanori*; Baba, Masaaki*; Hashimoto, Hideki*; Harjo, S.; Aizawa, Kazuya; et al.

Journal of Applied Physics, 131(13), p.134103_1 - 134103_7, 2022/04

 Times Cited Count:2 Percentile:16.92(Physics, Applied)

Journal Articles

Spin excitations coupled with lattice and charge dynamics in La$$_{2-x}$$Sr$$_{x}$$CuO$$_{4}$$

Ikeuchi, Kazuhiko*; Wakimoto, Shuichi; Fujita, Masaki*; Fukuda, Tatsuo; Kajimoto, Ryoichi; Arai, Masatoshi*

Physical Review B, 105(1), p.014508_1 - 014508_7, 2022/01

 Times Cited Count:3 Percentile:26.55(Materials Science, Multidisciplinary)

Journal Articles

Behavior of radiocesium in sediments in Fukushima coastal waters; Verification of desorption potential through pore water

Otosaka, Shigeyoshi*; Kambayashi, Shota*; Fukuda, Miho*; Tsuruta, Tadahiko; Misono, Toshiharu; Suzuki, Takashi; Aono, Tatsuo*

Environmental Science & Technology, 54(21), p.13778 - 13785, 2020/11

 Times Cited Count:16 Percentile:54.03(Engineering, Environmental)

Concentrations of $$^{137}$$Cs in seawater, seabed sediment, and pore water collected from the area around Fukushima were investigated from 2015 to 2018, and the potential of coastal sediments to supply radiocesium to the bottom environment was evaluated. The $$^{137}$$Cs concentration in the pore water ranged from 33 to 1934 mBq L$$^{-1}$$ and was 10-40 times higher than that in the overlying water (seawater overlying within 30 cm on the seabed). At most stations, the $$^{137}$$Cs concentrations in the overlying water and the pore water were approximately proportional to those in the sediment. The conditional partition coefficient between pore water and sediment was 0.9-14$$times$$10$$^{2}$$ L kg$$^{-1}$$, independent of the year of sampling. These results indicated that an equilibrium of $$^{137}$$Cs between pore water and sediment has established in a relatively short period, and $$^{137}$$Cs in the pore water is gradually exported to seawater near the seabed. A simple box model estimation based on these results showed that the $$^{137}$$Cs in the sediment was decreased by about 6% per year by desorption/diffusion of $$^{137}$$Cs from the seabed.

Journal Articles

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

 Times Cited Count:3 Percentile:14.77(Physics, Applied)

Journal Articles

Hard X-ray photoelectron spectroscopy study of Pt/Y$$_{3}$$Fe$$_{5}$$O$$_{12}$$

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

High energy X-ray photoelectron spectroscopy (HAXPES) measurements were carried out for the Spin Seebeck system Pt/Y$$_{3}$$Fe$$_{5}$$O$$_{12}$$(YIG). This system was found to show anomalous Hall effect, possible due to the formation of intermetallic compounds between Fe$$^{3+}$$ 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$$^{3+}$$ 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.

Journal Articles

Pyroelectric power generation from the waste heat of automotive exhaust gas

Kim, J.*; Yamanaka, Satoru*; Murayama, Ichiro*; Kato, Takanori*; Sakamoto, Tomokazu*; Kawasaki, Takuro; Fukuda, Tatsuo; Sekino, Toru*; Nakayama, Tadachika*; Takeda, Masatoshi*; et al.

Sustainable Energy & Fuels (Internet), 4(3), p.1143 - 1149, 2020/03

 Times Cited Count:21 Percentile:64.56(Chemistry, Physical)

Journal Articles

Lattice dynamics in FeSe via inelastic X-ray scattering and first-principles calculations

Murai, Naoki; Fukuda, Tatsuo; Nakajima, Masamichi*; Kawamura, Mitsuaki*; Ishikawa, Daisuke*; Tajima, Setsuko*; Baron, A. Q. R.*

Physical Review B, 101(3), p.035126_1 - 035126_6, 2020/01

 Times Cited Count:7 Percentile:35.48(Materials Science, Multidisciplinary)

We report an inelastic X-ray scattering investigation of phonons in FeSe superconductor. Comparing the experimental phonon dispersion with density functional theory (DFT) calculations in the non-magnetic state, we found a significant disagreement between them. A better overall agreement was obtained by allowing for spin-polarization in DFT calculations, despite the absence of magnetic order in FeSe. This calculation gives a realistic approximation, at DFT level, of the disordered paramagnetic state of FeSe, in which strong spin fluctuations are present.

Journal Articles

First determination of Pu isotopes ($$^{239}$$Pu, $$^{240}$$Pu and $$^{241}$$Pu) in radioactive particles derived from Fukushima Daiichi Nuclear Power Plant accident

Igarashi, Junya*; Zheng, J.*; Zhang, Z.*; Ninomiya, Kazuhiko*; Satou, Yukihiko; Fukuda, Miho*; Ni, Y.*; Aono, Tatsuo*; Shinohara, Atsushi*

Scientific Reports (Internet), 9(1), p.11807_1 - 11807_10, 2019/08

 Times Cited Count:24 Percentile:64.15(Multidisciplinary Sciences)

Radioactive particles were released into the environment during the Fukushima Dai-ichi Nuclear Power Plant (FDNPP) accident. Many studies have been conducted to elucidate the chemical composition of released radioactive particles in order to understand their formation process. However, whether radioactive particles contain nuclear fuel radionuclides remains to be investigated. Here, we report the first determination of Pu isotopes in radioactive particles. To determine the Pu isotopes ($$^{239}$$Pu, $$^{240}$$Pu and $$^{241}$$Pu) in radioactive particles derived from the FDNPP accident which were free from the influence of global fallout, radiochemical analysis and inductively coupled plasma-mass spectrometry measurements were conducted. Radioactive particles derived from unit 1 and unit 2 or 3 were analyzed. For the radioactive particles derived from unit 1, activities of $$^{239+240}$$Pu and $$^{241}$$Pu were (1.70-7.06)$$times$$10$$^{-5}$$ Bq and (4.10-8.10)$$times$$10$$^{-3}$$ Bq, respectively and atom ratios of $$^{240}$$Pu/$$^{239}$$Pu and $$^{241}$$Pu/$$^{239}$$Pu were 0.330-0.415 and 0.162-0.178, respectively. These ratios were consistent with the simulation results from ORIGEN code and measurements from various environmental samples. In contrast, Pu was not detected in the radioactive particles derived from unit 2 or 3. The difference in Pu contents is clear evidence towards different formation processes of radioactive particles, and detailed formation processes can be investigated from Pu analysis.

Journal Articles

Effect of magnetism on lattice dynamics in iron-based superconductors as seen via high-resolution inelastic X-ray scattering

Murai, Naoki; Fukuda, Tatsuo; Tajima, Setsuko*; Baron, A. Q. R.*

Hoshako, 32(4), p.199 - 208, 2019/07

Phonon spectra of detwinned SrFe$$_{2}$$As$$_{2}$$ crystals, as measured by inelastic X-ray scattering, show clear anisotropy accompanying the magneto-structural transition at 200 K. We model the modesplitting using magnetic DFT calculations, including a phenomenological reduction in force-constant anisotropy that can be attributed to magnetic fluctuations. This serves as a starting point for a general model of phonons in this material applicable to both magnetic and non-magnetic phase.

Journal Articles

Invariant incommensurate coherence length in spin-density-wave excitation of Cr$$_{0.99}$$Fe$$_{0.01}$$

Hiraka, Haruhiro*; Yano, Shinichiro*; Fukuda, Tatsuo

Journal of Magnetism and Magnetic Materials, 469, p.629 - 632, 2019/01

 Times Cited Count:0 Percentile:0.00(Materials Science, Multidisciplinary)

Journal Articles

Electrical and crystallographic study of an electrothermodynamic cycle for a waste heat recovery

Kim, J.*; Yamanaka, Satoru*; Nakajima, Akira*; Kato, Takanori*; Kim, Y.*; Fukuda, Tatsuo; Yoshii, Kenji; Nishihata, Yasuo; Baba, Masaaki*; Takeda, Masatoshi*; et al.

Advanced Sustainable Systems (Internet), 2(11), p.1800067_1 - 1800067_8, 2018/11

 Times Cited Count:8 Percentile:27.18(Green & Sustainable Science & Technology)

Journal Articles

Temperature stability of PIN-PMN-PT ternary ceramics during pyroelectric power generation

Moro, Takuya*; Kim, J.*; Yamanaka, Satoru*; Murayama, Ichiro*; Kato, Takanori*; Nakayama, Tadachika*; Takeda, Masatoshi*; Yamada, Noboru*; Nishihata, Yasuo; Fukuda, Tatsuo; et al.

Journal of Alloys and Compounds, 768, p.22 - 27, 2018/11

 Times Cited Count:18 Percentile:61.88(Chemistry, Physical)

161 (Records 1-20 displayed on this page)