Synchrotron X-Ray Absorption Spectroscopy (XAS) Studies on Structural and Magnetic Properties of T’-Pr2-xCexCuO4 Nanocrystals

2020 ◽  
Vol 855 ◽  
pp. 128-133
Author(s):  
Resky Irfanita ◽  
Putu Eka Dharma Putra ◽  
Bambang Triono ◽  
Malik Anjelh Baqiya ◽  
Darminto ◽  
...  
Keyword(s):  
Oxygen Vacancies ◽  
Bond Distance ◽  
Excess Oxygen ◽  
X Ray ◽  
Reduction Annealing ◽  
Gas Atmosphere ◽  
Successful Removal ◽  
Bond Distortion ◽  
Axis Length ◽  
X Ray Absorption

We have succeeded in synthesizing electron-doped cuprates T’-Pr2-xCexCuO4 (PCCO) with x = 0 and 0.10 nanocrystals prepared by the chemically dissolved method. Reduction annealing of the PCCO samples at 700°C under a flowing argon gas atmosphere has been performed for the removal of excess oxygen in the apical sites. The XRD data showed that the reduction annealing process decreases c-axis length indicating successful removal of the excess oxygen. The bond distortion of PCCO including coordination number and bond distance between the absorber atoms with the nearest neighboring atoms (Cu-O) was investigated by extended x-ray absorption fine structure (EXAFS) using Cu K-edge. The implication of our results is discussed on the basis of tremendous influence of oxygen vacancies on the magnetism of the nanosized T’-cuprates at the normal state.

Oxygen Reduction Effect on T’-Pr2-xCexCuO4 Nanopowders in the Underdoped Regime Studied by X-Ray Absorption near Edge Structure

2018 ◽  
Vol 936 ◽  
pp. 93-97 ◽  
Author(s):  
Irfanita Resky ◽  
Putu Eka Dharma Putra ◽  
Triono Bambang ◽  
Saiyasombat Chatree ◽  
Kamonsuangkasem Krongthong ◽  
...  
Keyword(s):  
Oxidation State ◽  
Oxidation States ◽  
Edge Structure ◽  
X Ray ◽  
Reduction Annealing ◽  
Gas Atmosphere ◽  
Reduction Effect ◽  
Ar Gas ◽  
X Ray Absorption ◽  
Cu Ions

This research is aimed to examine oxidation state of Copper (Cu) in both as-synthesized and reduced T’-Pr2-xCexCuO4 (T’-PCCO) with x = 0, 0.10, and 0.15 using Cu K-edge x-ray absorption near edge structure (XANES). The T‘-PCCO nanopowders were successfully synthesized by the chemically dissolved method with HNO3 as a dissolving agent continued by calcination at 1000°C for 15 h. The reduced T’-PCCO nanopowders were obtained by reduction annealing process at 700°C for 5 h under Ar gas atmosphere. The analyses of XANES spectra show that oxidation states of the Cu ions in all of the T'-PCCO nanopowders have values between +1 and +2. This indicates the existence of electron doping in the CuO2 planes, even in the undoped T’-structure. It is found that the oxidation states of the Cu ions change after reduction annealing depending on the existence of apical oxygen in the T'-structure. Based on the XANES analyses, it is revealed that the change of oxidation state is influenced by the presence of both electron and hole carriers in the two-carrier model of T’-structure.

Recovery of nanosize zinc from phosphor wastes with an ionic liquid

2009 ◽  
Vol 6 (3) ◽  
pp. 268 ◽  
Author(s):  
Hsin-Liang Huang ◽  
H. Paul Wang ◽  
Edward M. Eyring ◽  
Juu-En Chang
Keyword(s):  
Ionic Liquid ◽  
Absorption Spectroscopy ◽  
Room Temperature ◽  
Bond Distance ◽  
Extraction Process ◽  
Room Temperature Ionic Liquid ◽  
Zns Nanoparticles ◽  
Recovery Method ◽  
X Ray ◽  
X Ray Absorption

Environmental context. Very fine phosphor ashes are discharged from particulate collection systems (such as bag houses) in the cathode ray tube or television disassembling processes. Effective recovery of ZnO and ZnS nanoparticles from the phosphor ash can be achieved by extraction with a room temperature ionic liquid. By synchrotron radiation X-ray absorption spectroscopy, the obtained molecular scale data turn out to be very useful in revealing speciation of zinc in the extraction process, which also facilitates the development of a simple nanoparticle recovery method. Abstract. An effective, simple method has been developed for the recovery of ZnO and ZnS nanoparticles from hazardous phosphor ash waste. Experimentally, zinc (77%) in the phosphor ash (that contains mainly zinc (91%)) can be recovered by extraction with a room temperature ionic liquid (RTIL) ([C4mim][PF6], 1-butyl-3-methylimidazolium hexafluorophosphate). Component fitted X-ray absorption near edge structure (XANES) spectra of zinc indicate that metallic zinc (Zn) (9%) in the phosphor ash can be dissolved to form a Zn2+–1-methylimidazole ([mim]) complex during extraction with the RTIL. ZnS and ZnO nanoparticles (60–61%) can also be extracted from the phosphor. Over the 298–523 K temperature range, desired ZnO/ZnS ratios (0.3–0.6) can be obtained since interconversion of ZnS to ZnO in the RTIL is temperature dependent. The Fourier transformed extended X-ray absorption fine structure (EXAFS) data also show that the nanosize ZnS extracted in the RTIL possesses a Zn–S bond distance of 2.33 Å with coordination numbers (CNs) of 3.6–3.7. At 523 K, in the RTIL, ~30% of the ZnS is oxidised to form octahedral ZnO (with a bond distance of 2.10 Å and a CN of 6.1) that may coat the surfaces of the ZnS nanoparticles. This work exemplifies the utilisation of X-ray absorption spectroscopy (EXAFS and XANES) to reveal speciation and possible reaction pathways in a nanoparticle extraction process (with a RTIL) in detail.

scholarly journals Oxygen vacancies induced photoluminescence in $$\hbox {SrZnO}_2$$ nanophosphors probed by theoretical and experimental analysis

2020 ◽  
Vol 10 (1) ◽  
Author(s):  
Manju ◽  
Megha Jain ◽  
Saibabu Madas ◽  
Pargam Vashishtha ◽  
Parasmani Rajput ◽  
...  
Keyword(s):  
Density Functional Theory ◽  
Band Structure ◽  
Density Functional ◽  
Oxygen Vacancies ◽  
Defect States ◽  
Functional Theory ◽  
Edge Structure ◽  
X Ray ◽  
New Energy ◽  
X Ray Absorption

Abstract We report, for the first time, the influence of oxygen vacancies on band structure and local electronic structure of $$\hbox {SrZnO}_2$$ SrZnO 2 (SZO) nanophosphors by combined first principle calculations based on density functional theory and full multiple scattering theory, correlated with experimental results obtained from X-ray absorption and photoluminescence spectroscopies. The band structure analysis from density functional theory revealed the formation of new energy states in the forbidden gap due to introduction of oxygen vacancies in the system, thereby causing disruption in intrinsic symmetry and altering bond lengths in SZO system. These defect states are anticipated as origin of observed photoluminescence in SZO nanophosphors. The experimental X-ray absorption near edge structure (XANES) at Zn and Sr K-edges were successfully imitated by simulated XANES obtained after removing oxygen atoms around Zn and Sr cores, which affirmed the presence and signature of oxygen vacancies on near edge structure.

scholarly journals EXAFS analysis of uranium(IV) and thorium(IV) complexes in concentrated CaCl2 solutions

2011 ◽  
Vol 1 (1) ◽  
pp. 161-165
Author(s):  
A. Uehara ◽  
T. Fujii ◽  
H. Matsuura ◽  
N. Sato ◽  
T. Nagai ◽  
...  
Keyword(s):  
Aqueous Solution ◽  
Fine Structure ◽  
Coordination Number ◽  
Coordination Sphere ◽  
Perchloric Acid ◽  
Hydration Number ◽  
Bond Distance ◽  
X Ray ◽  
Acid Aqueous Solution ◽  
X Ray Absorption

Abstract The coordination of U4+ and Th4+ in concentrated CaCl2 solutions is studied by U and Th L III edge extended X-ray absorption fine structure (EXAFS) spectroscopy. With the decrease of concentration of CaCl2 from 6.9 to 4 M, the Cl− ion coordination number N Cl in the U4+ coordination sphere decreases from 3.4 to 1.3, while the hydration number N O increases from 4.5 to 6.7. The combined coordination number N O+NCl of U4+ in concentrated Cl− solution (8.0), is lower than that in 1.5 M perchloric acid aqueous solution (9.0). For Th4+, the decrease of concentration from 6.9 to 4 M CaCl2, the coordination number N Cl in the Th4+ coordination sphere decreased slightly from 1.9 to 1.5, while coordination number N O increased from 7.6 to 8.8. The N O+NCl of Th4+ in concentrated Cl− solution (9.0), is similar to that in 1.5 M perchloric acid. The bond distance of U–Cl (2.67 Å), is shorter than that of Th–Cl (2.76 Å), because of low coordination number N O to U4+. By adding HCl into the system, the U4+ and Th4+ coordination sphere is unchanged. The coordination structures of U4+ and Th4+ in concentrated LiCl is also discussed.

Oxygen Partial Pressure Dependence of In Situ X-Ray Absorption Spectroscopy at Co and Fe K-Edge for (La0.6Sr0.4)(Co0.2Fe0.8)O3–δ

2012 ◽  
Vol 9 (3) ◽  
Author(s):  
Takanori Itoh ◽  
Saori Shirasaki ◽  
Hironori Ofuchi ◽  
Sayaka Hirayama ◽  
Tetsuo Honma ◽  
...  
Keyword(s):  
Absorption Spectroscopy ◽  
Oxygen Vacancies ◽  
Ion Conductivity ◽  
Ion Conduction ◽  
Edge Structure ◽  
X Ray ◽  
Oxygen Ion Conductivity ◽  
Oxygen Ion ◽  
X Ray Absorption

(La0.6Sr0.4)(Co0.2Fe0.8)O3–δ (LSCF) has been promised as a cathode material of solid oxide fuel cells at intermediate temperatures. Despite the many previous studies of LSCF that have been reported, the role of Co and Fe atoms in the oxygen ion conduction is still unclear. In this work, we aimed at presenting each valence, oxygen chemical diffusion coefficient (Dchem) and activation energy (Ea) related to Co and Fe in LSCF by in situ X-ray absorption spectroscopy (XAS) at high temperatures and during reduction. For quantitative analysis of X-ray absorption near edge structure (XANES) spectroscopy, these results indicated that the Co valence decreased more easily than the Fe valence. On the other hand, from relaxation plots of the Co and Fe valence during reduction, the values of Dchem and Ea related to Co and Fe were nearly equal. Considering equations showing the oxygen ion conductivity, these results would indicate that oxygen ion conductivity was contributed by Co with more oxygen vacancies rather than Fe. According to these results, a structural model with and without oxygen vacancies and the oxygen ion conduction mechanism of LSCF was speculated, that is, we found that oxygen ion conductivity was more closely related to Co than Fe in LSCF by direct observations of in situ XAS.

scholarly journals Fluorescence-detected XAS with sub-second time resolution reveals new details about the redox activity of Pt/CeO2 catalyst

2018 ◽  
Vol 25 (4) ◽  
pp. 989-997 ◽  
Author(s):  
Alexander A. Guda ◽  
Aram L. Bugaev ◽  
Rene Kopelent ◽  
Luca Braglia ◽  
Alexander V. Soldatov ◽  
...  
Keyword(s):  
Time Resolution ◽  
Flow Reactor ◽  
Plug Flow ◽  
Redox Activity ◽  
Time Resolved ◽  
X Ray ◽  
Gas Atmosphere ◽  
Ceria Support ◽  
X Ray Absorption ◽  
Selective Oxidation Catalysts

A setup for fluorescence-detected X-ray absorption spectroscopy (XAS) with sub-second time resolution has been developed. This technique allows chemical speciation of low-concentrated materials embedded in highly absorbing matrices, which cannot be studied using transmission XAS. Using this setup, the reactivity of 1.5 wt% Pt/CeO2 catalyst was studied with 100 ms resolution during periodic cycling in CO- and oxygen-containing atmospheres in a plug-flow reactor. Measurements were performed at the Pt L 3- and Ce L 3-edges. The reactivity of platinum and cerium demonstrated a strong correlation. The oxidation of the catalyst starts on the ceria support helping the oxidation of platinum nanoparticles. The new time-resolved XAS setup can be applied to various systems, capable of reproducible cycling between different states triggered by gas atmosphere, light, temperature, etc. It opens up new perspectives for mechanistic studies on automotive catalysts, selective oxidation catalysts and photocatalysts.

scholarly journals Structural investigations of (Mn, Dy) co-doped ZnO nanocrystals using X-ray absorption studies

RSC Advances ◽  
2017 ◽  
Vol 7 (89) ◽  
pp. 56662-56675 ◽  
Author(s):  
N. Tiwari ◽  
S. Kumar ◽  
A. K. Ghosh ◽  
S. Chatterjee ◽  
S. N. Jha ◽  
...  
Keyword(s):  
Oxygen Vacancies ◽  
Sol Gel ◽  
Structural Investigations ◽  
X Ray ◽  
Magnetic Polarons ◽  
Zno Nanocrystals ◽  
Absorption Studies ◽  
Doped Zno ◽  
X Ray Absorption ◽  
Co Doped

EXAFS measurements on sol gel derived (Mn, Dy) co-doped ZnO nanocrystals show that oxygen vacancies are created near the Dy sites into ZnO lattice. Thus, oxygen vacancy assisted bound magnetic polarons contribute to the RTFM in the Dy doped samples.

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