Formation of structural defects and strain in electrodegraded Fe‐doped SrTiO₃ crystals due to oxygen vacancy migration

Abstract

We report on our investigation of structural defect and strain formation in electrodegraded reduced and oxidized, Fe‐doped SrTiO3 (Fe:STO) single crystals using optical second harmonic generation (SHG) and confocal Raman spectroscopy. SHG and Raman spectra reveal structural and electrochemical inhomogeneity resulting from the formation of Fe4+/oxygen ion and Fe3+/oxygen vacancy aggregation sites along the degraded anode and cathode interfaces, respectively. We show that mixed Fe3+/Fe4+ states and structural strain gradients are generated across the color fronts. These results, as well as oxygen sublattice differences between the anodic and cathodic bulk, present the color front as an interface between two dominant oxygen bonding distortions. The strain near the color front shows a strong dependence on oxygen vacancy concentration and diffusion within the crystals. Our characterization of structural and electrochemical changes due to electric field‐induced strain and oxygen vacancy migration advances knowledge of electrodegradation in perovskite‐based titanate single crystals.

RETRACTED: SrFexNi1−xO3−δ Perovskites Coated on Ti Anodes and Their Electrocatalytic Properties for Cleaning Nitrogenous Wastewater

“…In order to form more oxygen vacancies in SrNiO 3 perovskite and then enhance its electrocatalytic properties, ferrum (Fe) can be doped and partially substitute the Ni element in the B-site, because they have similar electronegativity (Fe: 1.8, Ni: 1.8) and atomic radii (Fe: 124.1 pm, Ni: 124.6 pm). Moreover, Fe (III) and Ni (IV) show different valence states in favor of delivering electrons and forming oxygen vacancies according to the electroneutrality principle [20]. Therefore, based on the above analysis, SrFe x Ni 1− x O 3−δ perovskites through doping Fe element into the SrNiO 3 perform the better conductivity and electrocatalytic activity.…”

Electrodeposited Trimetallic NiFeW Hydroxide Electrocatalysts for Efficient Water Oxidation

“…The O1s spectrum (Figure 5d) consists of intense peaks found at approximately 529.8 eV (metal‐oxygen bonds), 531.1 eV (oxygen defects), 532.5 eV (oxygen in hydroxide group), and 533.4 eV (chemisorbed water). The increased amount of oxygen defects in NiFeW1, NiFeW2, and NiFeW3 correspond to the partial valance states of W, and these oxygen vacancies are mostly consumed by the higher valence states of Ni and Fe ions [50] . Interestingly, the NiFeW2 sample not only presents the higher valence states of Ni and Fe (due to oxygen vacancies from non‐stoichiometric W oxides) but also consist of more catalytically active W 6+ sites, which are both essential to boost the OER performance.…”

“…The increased amount of oxygen defects in NiFeW1, NiFeW2, and NiFeW3 correspond to the partial valance states of W, and these oxygen vacancies are mostly consumed by the higher valence states of Ni and Fe ions. [50] Interestingly, the NiFeW2 sample not only presents the higher valence states of Ni and Fe (due to oxygen vacancies from non-stoichiometric W oxides) but also consist of more catalytically active W 6 + sites, which are both essential to boost the OER performance. Additionally, the broad X-band electron paramagnetic resonance (EPR) spectra confirm the defect structure in the NiFeW series compared to NiFe ( Figure S3).…”

Barium-Strontium Titanate/Porous Glass Structures for Microwave Applications

“…It is obvious that annealing in an oxygen atmosphere restores the missing oxygen in the crystal lattice and, as a result, reduces losses by two to three times. A change in the charge state of iron ions (as a result of oxidation from Fe 3+ to Fe 4+ ) may be another possible reason for the change in losses due to high-temperature treatment of iron-containing samples in oxygen [ 31 , 32 , 33 ].…”