Crystal structure of GdFeO3-type rare earth gallates and aluminates

Vasylechko, L.; Matkovskii, A.; Savytskii, D.; Suchocki, A.; Wallrafen, F.

doi:10.1016/s0925-8388(99)00247-9

Cited by 56 publications

(26 citation statements)

References 30 publications

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“…Manganese ions in YAlO 3 :Mn crystals as a rule are present in the form of Mn 4+ ions in octahedral coordination (Al 3+ positions) and Mn 2+ ions in strongly distorted dodecahedral coordination (Y 3+ positions) [1,[6][7][8][9]. The crystals being exposed to blue-green laser light show an intensive bluish-gray coloration caused by Mn 5+ ions created as a result of the Mn 4+ → Mn 5+ + e − photoionization process [1,2,6].…”

Section: Introductionmentioning

confidence: 99%

Effect of Manganese Concentration on Thermoluminescent Properties of YAlO₃:Mn Crystals

et al. 2010

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This work is devoted to experimental study of the effect of manganese concentration on thermoluminescent properties of YAlO3:Mn crystals grown by the Czochralski method. A new type of emitting centers beside of Mn 4+ and Mn 2+ ions was revealed at low concentration of manganese ions in the crystal. These centers are responsible for the high-temperature thermoluminescent peak at 570 K. A potential of this thermoluminescent peak for thermoluminescence dosimetry application is discussed.

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Section: Introductionmentioning

confidence: 99%

Effect of Manganese Concentration on Thermoluminescent Properties of YAlO₃:Mn Crystals

et al. 2010

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“…24 At room temperature, NGO is orthorhombic with a = 0.543 nm, b = 0.550 nm, c = 0.771 nm. 25 θ-2θ X-ray diffraction (XRD) scans of LSM-20 thin films on LAO and NGO are shown in Figure 1. The films show excellent hetero-epitaxial relationship due to the close lattice match between the thin film and substrate.…”

Section: Methodsmentioning

confidence: 99%

Surface Segregation in Lanthanum Strontium Manganite Thin Films and Its Potential Effect on the Oxygen Reduction Reaction

Davis

Ludwig

Smith

et al. 2017

J. Electrochem. Soc.

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A limiting factor for solid oxide fuel cell (SOFC) performance is the oxygen reduction reaction (ORR) that occurs at the cathode surface. This study examines changes in the surface composition of (La 0.8 Sr 0.2 ) 0.95 MnO 3 (LSM-20), a well-known SOFC cathode material. Heteroepitaxial thin films of LSM-20 were grown on lattice matched single crystal LaAlO 3 and NdGaO 3 substrates. Total Reflection X-ray Fluorescence (TXRF) measurements showed surface manganese enrichment on annealing at 800 • C in air. X-ray absorption near edge spectroscopy (XANES) showed that this leads to a redistribution of manganese 3+, 4+, and 2+ valence states at the surface. This was confirmed by defect modeling, which showed that surface Mn segregation leads to an increase in the surface concentration of oxygen vacancies and the Mn +4 species, both of which are expected to be beneficial for ORR. Solid oxide fuel cells (SOFCs) are chemical to electrical energy conversion devices that have several advantages, including potential efficiency over 70%, fuel flexibility, low emissions, and low degradation over long time scales.1 Commonly, SOFCs are operated at high temperatures (∼ 800• C). Incorporation of oxygen into the cell at the cathode surface, known as the oxygen reduction reaction (ORR) is identified as a rate-limiting step in an SOFC.2 The overall ORR can be expressed as:Equation 1 actually consists of several sub-steps including oxygen adsorption on the surface of the cathode, electron transfer to form oxygen ions, and incorporation of oxygen ions into oxygen vacancies, among others. For an electronic conducting cathode material like strontium-doped lanthanum manganite (LSM), the charge transfer occurs at the triple phase boundary (TPB), 2 requiring the adsorbed oxygen to be transported to the TPBs.Recent research examines how changes in cation dopant concentration impacts surface phase formation.3,4 Cations in these materials segregate to grain surfaces and create phases that can both enhance (as small, nanoscale adsorption sites) oxygen incorporation and block (large insulating phases) incorporation sites.Total reflection X-ray fluorescence (TXRF) studies on LSM films with 30 at% Sr A-site doping have suggested that strontium segregates to the surface and form strontium enriched nanoparticles.5 Yildiz et al. examined Mn K-edge XANES of LSM and saw no dependence on polarization at high temperature. Yildiz and coworkers also looked at La L III -edge XANES for LSM and LCM and suggested that there is an increase in the number of electronic La 5d-band vacancies in the near surface region of these materials. 15,20,21 In contrast, Shao-Horn and co-workers have shown that a low concentration of surface phases may in fact be beneficial to overall cell performance by promoting surface exchange.22 Understanding how the surface chemistry changes during initial heating may reveal a way to exploit the self-decorating nature of these materials. Thus, understanding surface segregation/phase formation at the cathode surface and their effects on t...

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“…The P nma structure can be thought of as being formed by repeated tilting of the VO 6 octahedral unit in a zigzag manner (GdFeO 3 -type distortion [51]) as shown in Fig. 1 as well as in an increase in the size of the unit cell from one formula unit (five atoms) for the cubic cell to four formula units (20 atoms) for the orthorhombic cell.…”

Section: A Structural Propertiesmentioning

confidence: 99%

“…The shifts in the infrared and Raman modes with respect to isotopic substitution are shown. 51 V is substituted by 54 V, 209 Bi is substituted by 212 Bi, and 16 O is substituted by 18 O. The oscillator strengths are normalized to unity.…”

Section: Infrared and Raman Spectramentioning

confidence: 99%

BiVO3 : A Bi-based material with promising uv-visible light absorption properties

et al. 2017

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Spin polarized density functional theory calculations on a predicted BiVO 3 crystal structure is presented. An orthorhombic phase with space group P nma is observed to be highly stable compared to the aristotype cubic structure. An optical band gap of 1.92 eV and a strong optical absorption at 2.25 eV-which lie in the visible region of the solar spectra-are estimated at the coupled-perturbed hybrid density-functional theory level. In addition, the band-structure analysis somewhat shows dispersion at the valence and conduction bands, and the binding energy of the excitons is calculated to be quite low, which can be possibly dissociated at room temperature. BiVO 3 is, therefore, expected to be a promising candidate worth being investigated for visible light driven photocatalytic applications. Simulated infrared and Raman spectra are reported, which could represent a guideline for future experiments, along with a full characterization of structural, electronic, and dynamic properties.

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Crystal structure of GdFeO3-type rare earth gallates and aluminates

Cited by 56 publications

References 30 publications

Effect of Manganese Concentration on Thermoluminescent Properties of YAlO₃:Mn Crystals

Effect of Manganese Concentration on Thermoluminescent Properties of YAlO₃:Mn Crystals

Surface Segregation in Lanthanum Strontium Manganite Thin Films and Its Potential Effect on the Oxygen Reduction Reaction

BiVO3 : A Bi-based material with promising uv-visible light absorption properties

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Crystal structure of GdFeO3-type rare earth gallates and aluminates

Cited by 56 publications

References 30 publications

Effect of Manganese Concentration on Thermoluminescent Properties of YAlO3:Mn Crystals

Effect of Manganese Concentration on Thermoluminescent Properties of YAlO3:Mn Crystals

Surface Segregation in Lanthanum Strontium Manganite Thin Films and Its Potential Effect on the Oxygen Reduction Reaction

BiVO3 : A Bi-based material with promising uv-visible light absorption properties

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Product

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Effect of Manganese Concentration on Thermoluminescent Properties of YAlO₃:Mn Crystals

Effect of Manganese Concentration on Thermoluminescent Properties of YAlO₃:Mn Crystals