Origin of Anomalous Lattice Expansion in Oxide Nanoparticles

Tsunekawa, Shin; Ishikawa, Kenji; Li, Z.-Q.; Kawazoe, Yoshiyuki; Kasuya, A.

doi:10.1103/physrevlett.85.3440

Cited by 440 publications

(318 citation statements)

References 19 publications

Supporting

Mentioning

286

Contrasting

Order By: Relevance

“…The reduction of cerium alone, without concurrent Frenkel defect accumulation, has been shown to result in structural modifications identical to those observed here 31,32 . As large Ce 3 þ cations (ionic radius ¼ 1.14 Å) replace Ce 4 þ (ionic radius ¼ 0.97 Å) 33 , the fluorite unit cell expands and the distribution of atoms of different ionic radii on the cation sublattice causes local structural distortion.…”

Section: Resultssupporting

confidence: 53%

Redox response of actinide materials to highly ionizing radiation

et al. 2015

View full text Add to dashboard Cite

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.

show abstract

Section: Resultssupporting

confidence: 53%

Redox response of actinide materials to highly ionizing radiation

et al. 2015

View full text Add to dashboard Cite

show abstract

“…This reveals that the lattice expansion in the NiO powder is occurred with the decrease of average crystallite size. Such observations were reported on similar metal oxide systems and attributed to strong repulsive interactions of parallel surface defect dipole, 21 the valence reduction, 30 unpaired electron orbitals at outer surface. 31 Figure 3 depicts the room temperature Raman spectra of pure NiO powders and as-milled powders under different milling speeds.…”

Section: Resultsmentioning

confidence: 69%

Enhanced room temperature ferromagnetism in antiferromagnetic NiO nanoparticles

2015

View full text Add to dashboard Cite

We report systematic investigations of structural, vibrational, resonance and magnetic properties of nanoscale NiO powders prepared by ball milling process under different milling speeds for 30 hours of milling. Structural properties revealed that both pure NiO and as-milled NiO powders exhibit face centered cubic structure, but average crystallite size decreases to around 11 nm along with significant increase in strain with increasing milling speed. Vibrational properties show the enhancement in the intensity of one-phonon longitudinal optical (LO) band and disappearance of two-magnon band due to size reduction. In addition, two-phonon LO band exhibits red shift due to size-induced phonon confinement effect and surface relaxation. Pure NiO powder exhibit antiferromagnetic nature, which transforms into induced ferromagnetic after size reduction. The average magnetization at room temperature increases with decreasing the crystallite size and a maximum moment of 0.016 μB/f.u. at 12 kOe applied field and coercivity of 170 Oe were obtained for 30 hours milled NiO powders at 600 rotation per minute milling speed. The change in the magnetic properties is also supported by the vibrational properties. Thermomagnetization measurements at high temperature reveal a well-defined magnetic phase transition at high temperature (TC) around 780 K due to induced ferromagnetic phase. Electron paramagnetic resonance (EPR) studies reveal a good agreement between the EPR results and magnetic properties. The observed results are described on the basis of crystallite size variation, defect density, large strain, oxidation/reduction of Ni and interaction between uncompensated surfaces and particle core with lattice expansion. The obtained results suggest that nanoscale NiO powders with high TC and moderate magnetic moment at room temperature with cubic structure would be useful to expedite for spintronic devices.

show abstract

“…75 The result is that the red shift and broadening observed in the Raman line is significantly larger than expected from the phonon confinement model and adequate fitting of the experimental spectra is only obtained when jointly considering the effects of inhomogeneous strain (associated to the dispersion in lattice constants as a consequence of the presence of vacancies and reduced cerium centers) 74 and phonon confinement. 63 A similar approach has been employed to explain qualitatively the shifts observed in the main band of Ce-Tb or Ce-Cu mixed oxide nanoparticles as a function of the Tb or Cu content.…”

Section: Raman Spectroscopymentioning

confidence: 94%

“…63 Thus, the analysis of the three-fold degenerated F 2g peak at 465 cm -1 (the only one allowed in first order) in CeO 2 nanosized samples with multidisperse size distributions requires consideration of both the effects of the presence of the vacancies (proposed to increase with decreasing particle size, at least for sizes below ca. 2 nm) 74 and the associated change in lattice dimensions. While the former, according to experimental evidence, is expected to give rise to blue shifts of the peak, this is compensated by the red shift produced upon lattice expansion (∆a), in accordance with the equation:…”

Section: Raman Spectroscopymentioning

confidence: 99%