Investigation of local structure effect and X-ray absorption characteristics (EXAFS) of Fe (Ti) K-edge on photocatalyst properties of SrTi(1−x)FexO(3−δ)

Ghaffari, Mohammad Ali; Liu, T.; Huang, Huilian; Tan, Ooi Kiang; Shannon, Mark A.

doi:10.1016/j.matchemphys.2012.06.037

Cited by 55 publications

(36 citation statements)

References 70 publications

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“…The obtained result is in a good agreement with results reported in literature [48,49] according to that Fe ions in STFO have mixture of Fe 3+ (Oh) and Fe 4+ (Oh) states. It should be also noted that according to [50] the Fe ions in STFO can have a mixed Fe 2+/ Fe 3+ (Oh +Td) oxidation state.…”

Section: Iron 2p X-ray Absorptionsupporting

confidence: 92%

Effect of Fe content on atomic and electronic structure of complex oxides Sr(Ti,Fe)O3−δ

et al. 2017

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We present a study of the electronic and atomic structure of two series of SrTi1-xFexO3-δ (STFO) powders with different Fe content produced by two different methods, spray pyrolysis or modified Pechini synthesis, by means of soft X-ray absorption spectroscopy. Partial substitution of Ti by Fe atoms in SrTiO3 were found to cause asymmetric distortion of TiO6 octahedrons which increases with increasing Fe content that may violate the cubic symmetry of STFO. The presence mainly of Fe 3+ states in octahedral environment at small concentration of Fe atoms along with essentially smaller content of Fe 4+ states in octahedral environment where the latter contribution increases with increasing Fe content was traced. It is found that the modified Pechini method allows to synthesize more stable structures but a tendency of the SrOx formation in the structure prepared by this technique was marked. The spray pyrolysis method gives the structure free of SrO precipitates but the presence of Fe 3+ states in tetrahedral environment with Fe content higher than 50% and even a certain amount of Fe 2+ ions in an octahedral environment at concentrations higher than 75% in the STFO prepared by this method was established. The O1s (K)-absorption spectra point to increase in oxygen vacancy concentration with increasing Fe content. The lowest degree of structure distortions with enough high oxygen vacancy concentration was traced in STFO (x= 0.25 to x = 0.35) produced by modified Pechini synthesis, which makes it mostly appropriate for technical applications, e.g., as gas sensors, oxygen separation membranes or as fuel cell material.

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Section: Iron 2p X-ray Absorptionsupporting

confidence: 92%

Effect of Fe content on atomic and electronic structure of complex oxides Sr(Ti,Fe)O3−δ

et al. 2017

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“…The peaks are located at 710.2 eV (Fe 2p 3/2 ) and 723.5 eV (Fe 2p 1/2 ), which are similar to those reported in a recent study of Fe 2p corresponding to the presence of Fe 3? [29]. The second doublet was located at 713.3 eV (Fe 2p 3/2 ) and 727.2 eV (Fe 2p 1/2 ) and assigned to Fe 4?…”

Section: Xps Analysismentioning

confidence: 99%

Structural characterisation of slightly Fe-doped SrTiO3 grown via a sol–gel hydrothermal synthesis

Fuentes

Muñoz

Barraza

et al. 2015

J Sol-Gel Sci Technol

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A detailed structural study of the incorporation of Fe into SrTiO 3 nanoparticles is reported. Slightly irondoped strontium titanate nanoparticles with 0, 1, 3 and 5 mol% concentration of iron were grown using a sol-gel hydrothermal process and characterised using Raman scattering, X-ray photoelectron and X-ray diffraction spectroscopy. The amorphisation of the nanostructures was observed as the iron content increased, which was confirmed by the TEM images. The XPS results indicated that the oxidation states of the Sr atoms were maintained in 2?. However, a mixture of Fe 3? and Fe 4? atoms was observed as the Fe content increased, resulting in a significant number of oxygen vacancies in the perovskite structure. The analysis of Raman spectra indicated that the intensity, linewidth and frequency shift of the TO 4 phonon can be used as an indicator of the Fe content as well as a local temperature probe for future thermal analysis. Graphical abstract Temperature evolution of the Raman spectra of STO:Fe 1 mol%. The peaks with star correspond to the second-order processes. (b) Temperature dependence of the TO 4 phonon mode. Blue dots denote measured Raman spectra, and the red solid lines are the Lorentzian fits to respective spectra.

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“…Despite their technological relevance, magnetic contributions to thermal expansion behavior of divalent substituted lanthanum ferrites have not yet been reported in the open literature. Substitution of divalent cations on the trivalent lanthanum A‐site creates a charge imbalance, which requires compensation through either the formation of oxygen vacancies or an increase in the iron valence from Fe 3+ to Fe 4+ . Although it is possible for Fe 4+ to disproportionate into a mixture of Fe 3+ and Fe 5+ in orthoferrite systems, this has only been observed below 200 K .…”

Section: Introductionmentioning

confidence: 99%

“…Substitution of divalent cations on the trivalent lanthanum A-site creates a charge imbalance, which requires compensation through either the formation of oxygen vacancies or an increase in the iron valence from Fe 3+ to Fe 4+ . 12,13 Although it is possible for Fe 4+ to disproportionate into a mixture of Fe 3+ and Fe 5+ in orthoferrite systems, this has only been observed below 200 K. 14,15 In addition to electronic and chemical changes, the different ionic radii of cation substitutions will affect the local structure of the material. Previous studies have reported that divalent, cation substitutions in LSF and LCF cause a reduction in the N eel temperatures, to~390°C for 10% Sr doped 4,16 and 350°C-400°C for 20% Ca doped.…”

Section: Introductionmentioning

confidence: 99%

Thermal Expansion of Alkaline‐Doped Lanthanum Ferrite Near the Néel Temperature

et al. 2013

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The thermal expansion and magnetic behaviors of divalent, alkaline-doped lanthanum ferrites (La0.9M0.1FeO3, M=Ca, Sr, Ba) were assessed using a combination of dilatometry, magnetometry, time-of-flight neutron diffraction, and high-temperature X-ray diffraction. Néel temperatures were determined through vibrating sample magnetometry and correlated well with changes in thermal expansion behavior observed during both dilatometry and X-ray diffraction. The Néel temperatures observed for pure, Ca-doped, Sr-doped, and Ba-doped lanthanum ferrites were 471°C, 351°C, 465°C, and 466°C, respectively. The effect of divalent substitutions on the magnetic behavior are attributed to charge compensation mechanisms and structural changes in the material

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Investigation of local structure effect and X-ray absorption characteristics (EXAFS) of Fe (Ti) K-edge on photocatalyst properties of SrTi(1−x)FexO(3−δ)

Cited by 55 publications

References 70 publications

Effect of Fe content on atomic and electronic structure of complex oxides Sr(Ti,Fe)O3−δ

Effect of Fe content on atomic and electronic structure of complex oxides Sr(Ti,Fe)O3−δ

Structural characterisation of slightly Fe-doped SrTiO3 grown via a sol–gel hydrothermal synthesis

Thermal Expansion of Alkaline‐Doped Lanthanum Ferrite Near the Néel Temperature

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