Experimental and theoretical interpretation of the order/disorder clusters in CeO2:La

Autor(es)

Rocha, Leandro Silva Rosa ^[1] ; Ciola Amoresi, Rafael Aparecido ^[2] ; Duarte, Thiago Marinho ^{[3, 4]} ; Marana, Naiara Leticia ^[3] ; Sambrano, Julio Ricardo ^[3] ; Aldao, Celso Manuel ^[5] ; Simoes, Alexandre Zirpoli ^[2] ; Ponce, Miguel Adolfo ^[5] ; Longo, Elson ^[1]

Afiliação do(s) autor(es)

^[1] Fed Univ Sao Carlos UFSCar, Dept Chem, Sao Carlos, SP - Brazil

^[2] Sao Paulo State Univ Unesp, Sch Engn, Guaratingueta, SP - Brazil

^[3] Sao Paulo State Univ UNESP, Sch Sci, Bauru, SP - Brazil

^[4] Univ Fed Paraiba, LACOM INCTMN, Joao Pessoa, Paraiba - Brazil

^[5] Inst Mat Sci & Technol INTEMA, Mar Del Plata - Argentina

• Tipo de documento: Artigo Científico
• Fonte: Applied Surface Science; v. 510, APR 30 2020.
• Citações Web of Science: 0

Resumo

A spectroscopic study of nanostructured lanthanum-doped cerium oxide samples showed that a mild decrease by 5.3% in the surface concentration of Ce(III) species and, a reduction by 0.2 eV in the so-called energy-gap (E-F-E-v) after lanthanum addition was sufficient to create the previously reported significant dual behavior when exposed to carbon monoxide at 653 K. The observed X-ray diffraction patterns indicated the presence of a pure fluorite-type crystalline structure. A higher presence of paramagnetic defects clusters, indicated by electron paramagnetic resonance spectroscopy measurements and confirmed by the X-ray photoelectron spectroscopy, was attributed as being responsible for its dual behavior in a CO(g) atmosphere. Theoretical studies have shown the band structure and density of state of the pure and doped material, illustrating the orbitals that participate in the valence band and conduction band. The addition of a small quantity of La3+ converted some CO3+ into Ce4+, narrowed the ``effective band-gap{''} by 0.2 eV, and created a singly ionized oxygen vacancy species, thus changing the total electrical resistance and creating its dual behavior. The exposure to a reducing atmosphere such as carbon monoxide resulted in a significant increase in defects and converted some Ce4+ into CO3+ and vice-versa with oxygen atmosphere exposure. (AU)

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