Influence of gadolinium doping on the structure and defects of ceria under fuel cell operating temperature

Abstract

Correlation between atomic positional shift, oxygen vacancy defects, and oxide ion conductivity in doped ceria system has been established in the gadolinium doped ceria system from X-ray diffraction (XRD) and Raman spectroscopy study at operating temperature (300–600 °C) of Intermediate Temperature Solid Oxide Fuel Cell (IT-SOFC). High temperature XRD data are used to quantify atomic positional shift from mean position with temperature. The Raman spectroscopy study shows additional vibration modes related to ordering of defect spaces (GdCe′−Vo••)* and (2GdCe′−Vo••)x generated due to association of oxygen vacancies and reduced cerium or dopant cations site (Gd3+), which disappear at 450 °C; indicating oxygen vacancies dissociation from the defect complex. The experimental evidences of cation-anion positional shifting and oxygen vacancies dissociation from defect complex in the IT-SOFC operating temperature are discussed to correlate with activation energy for ionic conductivity.

Sucrose‐nitrate auto combustion synthesis of Ce 0.85 Ln 0.10 Sr 0.05 O 2‐ δ (Ln = La and Gd) electrolytes for solid oxide fuel cells

“…These oxygen vacancies are referred to as extrinsic oxygen vacancies. However, the band at 640 cm −1 is ascribed to the oxygen vacancies which are formed due to the presence of some Ce 3+ ions in the samples and are referred to as intrinsic oxygen vacancies . Thus, the presence of bands at 550 and 640 cm −1 in the Raman spectrum of both the samples is a signature of the existence of oxygen vacancies in the synthesized samples.…”

Study of Filament Resistive Switching in New Pt/Co0.2TiO3.2/ITO Devices for Application in Non‐Volatile Memory

“…From the Raman spectrum we were able to observe six modes of phonons in 158 (F 2g ), 255 (E g ), 345 [T 2g (1)], 460 [T 2g (2)], 615 (A 1g ) e 701 (A 1g ) cm −1 , their respective assignments can be identified in the references . In particular to the A 1g ≈615 cm −1 mode, a widening that is attributed to intrinsic oxygen vacancies (represented in the deconvolution), which can be manifested by the coexistence of Co 3+ and Co 2+ ions, or also evidenced when in the structure inverse spinel (Co 2+ [Co 3+ Ti 4+ ]O 4 ) occupations of the octahedral sites of Ti 4+ by Co 3+ occurring with oxygen vacancies for local stabilization of charge . Thus, the results of Raman spectroscopy prove the presence of pre‐existing oxygen vacancies in CTO films.…”

Electronic Structure and Room Temperature Ferromagnetism in Gd‐doped Cerium Oxide Nanoparticles for Hydrogen Generation via Photocatalytic Water Splitting

“…These peaks are assigned to defect space that include intrinsic oxygen vacancies due to nonstoichiometry of CeO 2 . The three possible defect induced mechanism for oxygen vacancies in pure CeO 2 sample can be given as…”

“…The possible disorder mechanism for extrinsic oxygen vacancies in Ce 1− x Gd x O 2 ( x = 0.02, 0.04, 0.06, 0.08, and 0.10) NPs can be given aswhere symbols have the following meaning as: and are Ce 4+ and Gd 3+ ions on the CeO 2 lattice site, respectively, is O −2 ions on an oxygen lattice site, and is neutral oxygen vacancy site. In addition, another vacancy peak can also be observed in the range of 598–600.1 cm −1 , which is assigned to the defect space including intrinsic oxygen vacancies due to reduction of Ce 4+ to Ce 3+ , i.e., nonstoichiometry of ceria . The possible disorder reaction for intrinsic oxygen vacancies in the sample can be given aswhere symbols have the following meaning as: and are Ce 4+ and Ce 3+ ions on the Ce lattice site, respectively, is O −2 ions on an oxygen lattice site, and …”

“…[61] These peaks are assigned to defect space that include intrinsic oxygen vacancies due to nonstoichiometry of CeO 2 . The three possible defect induced mechanism for oxygen vacancies in pure CeO 2 sample can be given as [62]…”