Disentangling small-polaron and Anderson-localization effects in ceria: Combined experimental and first-principles study

Kolodiazhnyi, Taras; Tipsawat, Pannawit; Charoonsuk, Thitirat; Kongnok, Thanundon; Jungthawan, Sirichok; Suthirakun, Suwit; Vittayakorn, Naratip; Maensiri, Santi

doi:10.1103/physrevb.99.035144

Phys. Rev. B

2019

DOI: 10.1103/physrevb.99.035144

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Disentangling small-polaron and Anderson-localization effects in ceria: Combined experimental and first-principles study

Taras Kolodiazhnyi

Pannawit Tipsawat

Thitirat Charoonsuk

et al.

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Cited by 3 publications

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“… 13 The results were interpreted as being due to an enhanced polarization field following the removal of oxygen atoms from the lattice. 14 − 16 In this picture, the functionality of cerium oxide is linked to the mobility of oxygen ions, in turn entangled with carrier mobility via polaron hopping. 15 , 17 …”

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confidence: 99%

“…In particular, the presence of small polarons in CeO 2 was suggested by the temperature dependence of the conductivity of single crystals and supported using the thermopower-conductivity relation . The results were interpreted as being due to an enhanced polarization field following the removal of oxygen atoms from the lattice. − In this picture, the functionality of cerium oxide is linked to the mobility of oxygen ions, in turn entangled with carrier mobility via polaron hopping. , …”

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confidence: 99%

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Ultrafast Formation of Small Polarons and the Optical Gap in CeO₂

Cresi

Mario

Catone

et al. 2020

J. Phys. Chem. Lett.

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The ultrafast dynamics of excited states in cerium oxide are investigated to access the early moments of polaron formation, which can influence the photocatalytic functionality of the material. UV transient absorbance spectra of photoexcited CeO 2 exhibit a bleaching of the band edge absorbance induced by the pump and a photoinduced absorbance feature assigned to Ce 4f → Ce 5d transitions. A blue shift of the spectral response of the photoinduced absorbance signal in the first picosecond after the pump excitation is attributed to the dynamical formation of small polarons with a characteristic time of 330 fs. A further important result of our work is that the combined use of steady-state and ultrafast transient absorption allows us to propose a revised value for the optical gap for ceria ( E og = 4 eV), significantly larger than usually reported.

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confidence: 99%

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confidence: 99%

Ultrafast Formation of Small Polarons and the Optical Gap in CeO₂

Cresi

Mario

Catone

et al. 2020

J. Phys. Chem. Lett.

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Electrical conductivity, magnetism, and optical properties of reduced $$\hbox {BaCeO}_3$$BaCeO3

2019

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Atomic-scale environment of niobium in ore minerals as revealed by XANES and EXAFS at the Nb K-edge

Bollaert,

Chassé,

Morin

et al. 2024

Eur. J. Mineral.

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Abstract. The mineralogy of niobium (Nb) is characterized by multicomponent oxides such as AB2O6, A2B2O7, ABO4, and ABO3 in which Nb is incorporated in the B site. Such complex crystal-chemistry prevents their unambiguous identification in ore deposits such as hydrothermal rocks and laterites which exhibit complex and fine-grained textures. The understanding of the processes controlling Nb ore deposit formation in various geological settings is therefore limited, although Nb is a critical element. In this study, we use X-ray absorption spectroscopy (XAS) at the Nb K-edge to investigate the local atomic-scale structure around Nb in a large set of natural and synthetic minerals of geological and technological importance. Our X-ray absorption near-edge structure (XANES) data at the Nb K-edge show three major features of variable position and intensity and then can be related to the local distortion and coordination number of the Nb site. Shell-by-shell fits of the extended X-ray absorption fine structure (EXAFS) data reveal that the NbO6 octahedra are distorted in a variety of pyrochlore species. At least two distinct first shells of O atoms are present while reported crystallographic data yield regular octahedra in the same minerals. Next-nearest Nb–Nb distances in pyrochlore and Nb-bearing perovskite mirror a corner-sharing NbO6 network, whereas the two Nb–Nb distances in columbite are typical of edge- and corner-sharing NbO6 octahedra. Such a resolution on the Nb site geometry and the intersite relationships between the next-nearest NbO6 octahedra is made possible by collecting EXAFS data under optimal conditions at 20 K and up to 16 Å−1. The local structure around substituted Nb5+ in Fe3+, Ti4+, and Ce4+ oxides suffers major changes relative to the unsubstituted structures. The substitution of Nb5+ for Ti4+ in anatase leads to the increase in the interatomic distances between Nb and its first and second Ti4+ neighbors. The substitution of Nb5+ for Ce4+ in cerianite reduces the coordination number of the cation from eight to four, and the Nb–O bonds are shortened compared to Ce–O ones. In hematite, Nb5+ occupies a regular site, whereas the Fe3+ site is strongly distorted suggesting major site relaxation due to charge mismatch. The sensitivity of XANES and EXAFS spectroscopies at the Nb K-edge to the local site geometry and next-nearest neighbors demonstrated in this study would help decipher Nb speciation and investigate mineralogical reactions of Nb minerals in deposit-related contexts such as hydrothermal and lateritic deposits.

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Disentangling small-polaron and Anderson-localization effects in ceria: Combined experimental and first-principles study

Cited by 3 publications

References 41 publications

Ultrafast Formation of Small Polarons and the Optical Gap in CeO₂

Ultrafast Formation of Small Polarons and the Optical Gap in CeO₂

Electrical conductivity, magnetism, and optical properties of reduced $$\hbox {BaCeO}_3$$BaCeO3

Atomic-scale environment of niobium in ore minerals as revealed by XANES and EXAFS at the Nb K-edge

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Disentangling small-polaron and Anderson-localization effects in ceria: Combined experimental and first-principles study

Cited by 3 publications

References 41 publications

Ultrafast Formation of Small Polarons and the Optical Gap in CeO2

Ultrafast Formation of Small Polarons and the Optical Gap in CeO2

Electrical conductivity, magnetism, and optical properties of reduced $$\hbox {BaCeO}_3$$BaCeO3

Atomic-scale environment of niobium in ore minerals as revealed by XANES and EXAFS at the Nb K-edge

Contact Info

Product

Resources

About

Ultrafast Formation of Small Polarons and the Optical Gap in CeO₂

Ultrafast Formation of Small Polarons and the Optical Gap in CeO₂