Temat: 61.72.J- - Katalog OPAC zbiorów

Skocz do pozycji: 1.

Tytuł:: Effect of $Fe^{2+} (Fe^{3+})$ Doping on Structural Properties οf $CeO_2$ Nanocrystals
Autorzy:: Radović, M.
Dohčević-Mitrović, Z.
Paunović, N.
Šćepanović, M.
Matović, B.
Popović, Z.
Powiązania:: https://bibliotekanauki.pl/articles/1807838.pdf
Data publikacji:: 2009-07
Wydawca:: Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:: 61.72.uj
78.30.-j
75.50.Tt
Opis:: We have measured the Raman scattering and magnetization of pure and $Fe^{2+}(Fe^{3+})$ doped $CeO_2$ nanopowders at room temperature. The Raman scattering spectra revealed the existence of $CeO_2$ fluorite cubic structure for all investigated samples. The Raman active mode at about 600 $cm^{-1}$, seen in all samples, can be ascribed to the $CeO_2$ intrinsic oxygen vacancies. Additional Raman modes at 720 $cm^{-1}$, 1320 $cm^{-1}$ and 1600 $cm^{-1}$, which appear in the spectra of doped samples, can be assigned to maghemite $(γ-Fe_2O_3)$ cation deficient structure, to $2ω_{LO}$ IR-allowed overtone and two magnon structure, respectively. This implies that our powders are composed of mixed valence states and have defective structure. Presence of oxygen defect states and magnetic ions can be responsible for the observed ferromagnetism at room temperature in both pure and Fe doped samples.
Źródło:: Acta Physica Polonica A; 2009, 116, 1; 84-87
0587-4246
1898-794X
Pojawia się w:: Acta Physica Polonica A
Dostawca treści:: Biblioteka Nauki

Artykuł

Skocz do pozycji: 2.

Tytuł:: Anharmonicity Effects in Nanocrystals Studied by Raman Scattering Spectroscopy
Autorzy:: Dohčević-Mitrović, Z.
Popović, Z.
Šćepanović, M.
Powiązania:: https://bibliotekanauki.pl/articles/1807800.pdf
Data publikacji:: 2009-07
Wydawca:: Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:: 63.22.-m
78.67.Bf
78.30.-j
61.72.uj
Opis:: Phonon-phonon interactions were investigated in various nanocrystalline powders like anatase $TiO_{2-δ}$, pure $CeO_{2-δ}$ and ceria doped with Nd(Gd) analyzing temperature dependent Raman spectra of these systems. Phonon confinement model based on size, inhomogeneous strain and anharmonic effects was used to properly describe the evident changes present in the Raman spectra of pure and doped ceria nanocrystalline samples. In small particles of pure and doped ceria nanocrystals, when size effects have minor impact on Raman modes, four phonon anharmonic processes prevail under the three-phonon ones. When nanopowdered particles are grown enough size effects provoke changes of the anharmonic interactions when three-phonon coupling prevails over the four-phonon anharmonic processes. In nanocrystalline anatase $TiO_2$ evident blueshift of the most prominent $E_g$ Raman mode probably originates from dominant four-phonon anharmonic interactions.
Źródło:: Acta Physica Polonica A; 2009, 116, 1; 36-41
0587-4246
1898-794X
Pojawia się w:: Acta Physica Polonica A
Dostawca treści:: Biblioteka Nauki

Artykuł

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