Study on the behavior of oxygen atoms in swift heavy ion irradiated CeO2 by means of synchrotron radiation X-ray photoelectron spectroscopy

Iwase, A.; Ohno, Hideo; Ishikawa, N.; Baba, Yuji; Hirao, Naohisa; Sonoda, Tatsuhiko; Kinoshita, Motoyasu

doi:10.1016/j.nimb.2009.02.035

Cited by 43 publications

(34 citation statements)

References 8 publications

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“…The roughly 2 eV edge shift, which also does not vary significantly between the two ions, indicates partial reduction, as a complete reduction of all Ce 4 þ to Ce 3 þ corresponds to a 7 eV shift 30 . Previous studies 17,18 of CeO 2 irradiated with 200 MeV Xe ions have demonstrated similar oxidation state changes using X-ray photoelectron spectroscopy.…”

Section: Resultsmentioning

confidence: 59%

“…Although radiation-induced redox effects have been observed in previous studies 14,[17][18][19]44 , this comparative investigation of both valence state changes and structural damage caused by irradiation, in a range of materials, represents the first demonstration of systematic coupling between the two modifications. Reducible materials, with multivalent cations, show structural radiation responses that are fundamentally different from that of non-redox active ThO 2 .…”

Section: Discussionmentioning

confidence: 68%

“…They attribute this track size discrepancy to the production of a small, vacancy-rich track core (visible in STEM micrographs) surrounded by a large, interstitialrich track shell (observed with conventional TEM). Comparison of these STEM results with X-ray photoelectron spectroscopy and extended X-ray absorption fine structure studies 17,18 of irradiated CeO 2 indicate that the segregation of defects occurs preferentially on the oxygen sublattice, resulting in a hypostoichiometric track core and a hyperstoichiometric shell. Consistent with our results, this suggests that damage accumulation in this reducible material is driven by concurrent cation valence changes and anion-specific Frenkel pair formation, a process distinct from that of nonreducible ThO 2 .…”

Section: Resultsmentioning

confidence: 86%

“…2 must be at least partially attributed to the effects of the observed cerium valence reduction. Comparison of quantitative unit cell expansion and valence reduction data by Iwase et al 18 indicates that the expansion induced in CeO 2 by ions in the electronic stopping regime can be almost entirely attributed to this redox effect. The lack of a significant influence of ion mass and energy on the extent to which cerium is reduced to the trivalent state explains the constant damage saturation in this material and further suggests that this redox effect is the primary cause of the observed structural modifications.…”

Section: Resultsmentioning

confidence: 95%

“…It is generally assumed that electron-hole recombination leads to recovery of the pre-irradiation charge distribution 13 but, given the highly nonequilibrium conditions under which relaxation of the electron cascade occurs, electronic structure modifications are possible. Of particular interest is the influence of complex f-electron chemistry on a material's radiation response, considering previous work 17,18 reporting the reduction of Ce 4 þ to Ce 3 þ , following exposure of CeO 2 to ionizing radiation. In addition, the reduction of Zr 4 þ to Zr 3 þ has been shown 19 to accompany a radiation-induced phase transformation in Sc 4 Zr 3 O 12 (ref.…”

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confidence: 99%

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Redox response of actinide materials to highly ionizing radiation

et al. 2015

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Energetic radiation can cause dramatic changes in the physical and chemical properties of actinide materials, degrading their performance in fission-based energy systems. As advanced nuclear fuels and wasteforms are developed, fundamental understanding of the processes controlling radiation damage accumulation is necessary. Here we report oxidation state reduction of actinide and analogue elements caused by high-energy, heavy ion irradiation and demonstrate coupling of this redox behaviour with structural modifications. ThO 2 , in which thorium is stable only in a tetravalent state, exhibits damage accumulation processes distinct from those of multivalent cation compounds CeO 2 (Ce 3 þ and Ce 4 þ ) and UO 3 (U 4 þ , U 5 þ and U 6 þ ). The radiation tolerance of these materials depends on the efficiency of this redox reaction, such that damage can be inhibited by altering grain size and cation valence variability. Thus, the redox behaviour of actinide materials is important for the design of nuclear fuels and the prediction of their performance.

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Section: Resultsmentioning

confidence: 59%

Section: Discussionmentioning

confidence: 68%

Section: Resultsmentioning

confidence: 86%

Section: Resultsmentioning

confidence: 95%

mentioning

confidence: 99%

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Redox response of actinide materials to highly ionizing radiation

et al. 2015

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Hole‐blocking mechanism in high‐gain avalanche rushing amorphous photoconductor (HARP) film

Kikuchi¹,

Ohkawa²,

Miyakawa

et al. 2011

Phys. Status Solidi C

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HARP photoconductive film made of amorphous selenium (a‐Se), which makes use of the avalanche multiplication phenomenon, has been developed for the ultrahigh‐sensitivity television cameras that are used to report breaking news at night or to produce nature and science programs. We have tried to reveal the hole‐blocking mechanism in HARP films in the present work to improve their characteristics. It is important to reduce the dark current in HARP film to improve its sensitivity. HARP film has a hole‐blocking layer to suppress dark current, which interrupts the injection of holes to the a‐Se layer. Hole injection is considered one of the main factors related to dark current. The hole‐blocking layer consists of cerium dioxide (CeO2), which is an n‐type wide‐gap material. We have recently succeeded in producing improved CeO2 whose hole‐blocking capabilities are superior to the abilities of conventional normal CeO2. This paper describes the hole‐blocking mechanism in HARP film. To investigate this, the relationship between dark current and the film thickness of the CeO2 layer were measured with each HARP film using the two different types of CeO2. Furthermore, we analyzed the Ce 3d core‐level photoemission spectra for both types of CeO2 layers in HARP film by using hard X‐ray photoelectron spectroscopy (HAX‐PES) at Spring‐8. As a result, we found that the hole‐blocking capabilities of the film could be improved by reducing the number of defect levels generated from oxygen vacancies in the CeO2 hole‐blocking layer (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

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