DEFECT STRUCTURE IN "SOFT" (Gd,Fe)-CODOPED PZT 52.5/47.5 PIEZOELECTRIC CERAMICS

2008 ◽  
Vol 01 (01) ◽  
pp. 7-11 ◽  
Author(s):  
EMRE ERDEM ◽  
MICHAEL D. DRAHUS ◽  
RÜDIGER-A. EICHEL ◽  
HANS KUNGL ◽  
MICHAEL J. HOFFMANN ◽  
...  
Keyword(s):  
Electron Paramagnetic Resonance ◽  
Defect Structure ◽  
Charge Compensation ◽  
The Other ◽  
Partial Charge ◽  
Paramagnetic Resonance ◽  
Defect Dipole ◽  
Paramagnetic Probe ◽  
A Site ◽  
Electron Paramagnetic

Ferroelectric 1 mol% Gd 3+ and 0.5 mol% Fe 3+ codoped "soft" Pb [ Zr 0.525 Ti 0.475] O 3 ceramics were studied by means of multifrequency electron paramagnetic resonance (EPR) spectroscopy. The obtained results prove that iron is incorporated at the [ Zr , Ti ]-site, acting as an acceptor and building a charged [Formula: see text] defect dipole with a directly coordinated oxygen vacancy for partial charge compensation. As the La 3+ ion is diamagnetic, no information is accessible about the donor. Gd 3+ is an isoelectronic and paramagnetic probe for studying A-site. On the other hand, the donor forms no defect associates with lattice vacancies and rather exists as an "isolated" functional center. Consequently, also the lead vacancies that are created for charge compensation have to exist as isolated centers in compound.

scholarly journals Simulation of the electron-paramagnetic-resonance spectrum of the iron-protein of nitrogenase. A prediction of the existence of a second paramagnetic centre

1978 ◽  
Vol 175 (3) ◽  
pp. 955-957 ◽  
Author(s):  
D J Lowe
Keyword(s):  
Electron Paramagnetic Resonance ◽  
Electron Paramagnetic Resonance Spectrum ◽  
Complex Formation ◽  
Resonance Spectrum ◽  
The Other ◽  
Paramagnetic Centre ◽  
Paramagnetic Resonance ◽  
Iron Protein ◽  
Integrated Intensities ◽  
Electron Paramagnetic

The e.p.r. spectra of the Fe-proteins of nitrogenase from all sources studied have unusual features in that they have very anisotropic linewidths and low integrated intensities. These characteristics can be explained by assuming that one of the two electrons accepted by these proteins is located at a rapidly relaxing paramagnetic centre that is unobservable by e.p.r., but causes anisotropic broadening of the e.p.r. signal of the other electron. Complex-formation between Fe-proteins and MgATP is described in terms of a 50-60 degrees rotation of the e.p.r.-observable centre.

scholarly journals Copper Complexes of Benzoylacetone Bis-Thiosemicarbazones: Metal and Ligand Based Redox Reactivity

2021 ◽  
Vol 74 (1) ◽  
pp. 34 ◽  
Author(s):  
Jessica K. Bilyj ◽  
Jeffrey R. Harmer ◽  
Paul V. Bernhardt
Keyword(s):  
Electron Paramagnetic Resonance ◽  
Cyclic Voltammetry ◽  
Copper Complexes ◽  
Atmospheric Oxygen ◽  
The Other ◽  
Oxidation Reactions ◽  
Paramagnetic Resonance ◽  
Time Resolved ◽  
Vis Spectroscopy ◽  
Electron Paramagnetic

Bis-thiosemicarbazones derived from the β-diketone benzoylacetone (H3banR, R=Me, Et, Ph) are potentially tetradentate N2S2 ligands whose coordination chemistry with copper is reported. In the absence of oxygen and in the presence of base they form anionic CuII complexes of the fully deprotonated ligands [CuII(banR)]–. Upon exposure to atmospheric oxygen they undergo a complex series of reactions leading to two types of products; one a ligand oxidised ketone complex [CuII(banRO)] and the other an unprecedented dimeric di-CuIII complex [(CuIII(banR))2] depending on the R substituent. Time-resolved UV-vis spectroscopy, cyclic voltammetry, spectroelectrochemistry, and electron paramagnetic resonance (EPR) spectroscopy have been used to identify intermediates on the way to stable products formed under both anaerobic and aerobic conditions. It is found that both ligand-centred and Cu-centred oxidation reactions are occurring in parallel leading to this unusually complicated mixture of products.

Theoretical Studies on the Gyromagnetic Factors and the Hyperfine Structure Constants for the Tetragonal Copper Center in KTaO3

2005 ◽  
Vol 60 (8-9) ◽  
pp. 615-618 ◽  
Author(s):  
Hui-Ning Dong
Keyword(s):  
Experimental Data ◽  
Electron Paramagnetic Resonance ◽  
Hyperfine Structure ◽  
Defect Structure ◽  
Electrostatic Repulsion ◽  
Theoretical Studies ◽  
Paramagnetic Resonance ◽  
Copper Center ◽  
Structure Constants ◽  
Electron Paramagnetic

The gyromagnetic factors g∥, g⊥ and the hyperfine structure constants A∥ and A⊥ of the tetragonal Cu2+ center in KTaO3 are theoretically studied in this work. Based on the analyses of the electron paramagnetic resonance results of this center, it is found that the impurity Cu2+ occupies the octahedral Ta5+ site, associated with a nearest-neighbouring oxygen vacancy VO along the C4 axis. Due to the electrostatic repulsion of VO, Cu2+ is displaced away from VO by ΔZ(≈ −0.29 Å ) along the C4 axis. The theoretical values of the g and A factors based on the above defect structure and the impurity displacement agreee reasonably with the experimental data.

Fe3+defect dipole centers in ferroelectricPbTiO3studied using electron paramagnetic resonance

2009 ◽  
Vol 80 (1) ◽  
Author(s):  
D. J. Keeble ◽  
M. Loyo-Menoyo ◽  
Z. I. Y. Booq ◽  
R. R. Garipov ◽  
V. V. Eremkin ◽  
...  
Keyword(s):  
Electron Paramagnetic Resonance ◽  
Paramagnetic Resonance ◽  
Defect Dipole ◽  
Electron Paramagnetic

Two-Way Electron Paramagnetic Resonance (EPR) Cavity and Stark Effect on Nitrogen Oxide

1980 ◽  
Vol 34 (3) ◽  
pp. 296-299
Author(s):  
Isao Suzuki ◽  
Yoshihisa Kaneko
Keyword(s):  
Electron Paramagnetic Resonance ◽  
Electric Field ◽  
Nitrogen Oxide ◽  
Electric Dipole ◽  
Stark Effect ◽  
Dipole Transition ◽  
The Other ◽  
Sample Cell ◽  
Paramagnetic Resonance ◽  
Electron Paramagnetic

A two-way electron paramagnetic resonance cavity for magnetic dipole transition (MDT) and electric dipole transition (EDT) was manufactured. There are two openings to fit the sample cell for MDT and for EDT in the cylindrical TE011 mode. One opening is located on the axis of the cavity and the other is located away from the axis. EPR spectra obtained from the mixture of oxygen and nitrogen oxide when the sample cell was inserted in each opening showed the selective transition of the MDT or of the EDT of the species. When dc electric field parallel to the steady magnetic field was applied to the nitrogen oxide located away from the axis, each of the EDT peaks was divided into two peaks, one of which was higher than the other. The magnitude of the splitting was proportional to the electric field strength, in agreement with the theory. The permanent electric dipole moment 0.159 × 10−18 cgs esu obtained agreed with the value reported in the literature.

scholarly journals Coupling of [33S]sulphur to molybdenum(V) in different reduced forms of xanthine oxidase

1981 ◽  
Vol 199 (3) ◽  
pp. 629-637 ◽  
Author(s):  
J P G Malthouse ◽  
G N George ◽  
D J Lowe ◽  
R C Bray
Keyword(s):  
Electron Paramagnetic Resonance ◽  
Xanthine Oxidase ◽  
The Other ◽  
Reduced Form ◽  
Sulphur Atom ◽  
Paramagnetic Resonance ◽  
Different Types ◽  
Resonance Coupling ◽  
Electron Paramagnetic ◽  
Reduced Forms

Different reduced forms of xanthine oxidase, labelled specifically in the cyanide-labile site with 33S, were prepared and examined by electron paramagnetic resonance. Coupling of this isotope to molybdenum(V) was quantified with the help of computer simulations and found to differ markedly from one reduced form to another. The xanthine Very Rapid signal shows strong, highly anisotropic, coupling with A(33S)av. 1.27 mT. For this signal, axes of the g- and A(33S)-tensors are rotated relative to one another. One axis of the A-tensor is in the plane of gxx ang gyy, but rotated by 40 degrees relative to the gxx axis, whereas the direction of weakest coupling to sulphur deviates by 10 degrees from the gzz axis. In contrast with this signal, only rather weaker coupling was observed in different types of Rapid signal [A(33S)av. 0.3--0.4 mT], and in the Inhibited signal coupling was weaker still [A(33S)av. 0.1--0.2 mT]. Clearly, there must be substantial differences in the structures of the molybdenum centre in the different signal-giving species, with the sulphur atom perhaps in an equatorial type of ligand position in the Very Rapid species but in a more axial one in the other species. Structures are discussed in relation to the mechanism of action of the enzyme and the nature of the proton-accepting group that participates in turnover.

EPR AND MAGNETIC SUSCEPTIBILITY STUDIES OF V4+ IONS IN 2B2O3·SrO GLASS MATRIX

2002 ◽  
Vol 16 (19) ◽  
pp. 2807-2813 ◽  
Author(s):  
I. ARDELEAN ◽  
O. COZAR ◽  
C. CRACIUN ◽  
C. CEFAN
Keyword(s):  
Electron Paramagnetic Resonance ◽  
Magnetic Susceptibility ◽  
Glass Matrix ◽  
The Other ◽  
Magnetic Data ◽  
Broad Line ◽  
Paramagnetic Resonance ◽  
Paramagnetic Curie Temperature ◽  
Electron Paramagnetic ◽  
Lcao Mo

Electron paramagnetic resonance (EPR) and magnetic susceptibility studies on x V 2 O 5 ·(100 - x)[2 B 2 O 3 · SrO ] glasses with 0 ≤ x ≤ 30 mol% were performed. The covalence degree of vanadium bonds was estimated according to the LCAO-MO model. The EPR data show the presence of V4+ ions in a square-pyramidal coordination (C4v). The experimental EPR spectra are simulated assuming a superposition of two signals, one with hyperfine structure (HFS) typical for isolated ions and the other one consists of a broad line without HFS characteristic for clustered ions. These results are consistent with the magnetic data which indicate that for x ≥ 5 mol% V2O5 the temperature dependence of the reciprocal magnetic susceptibility is described by a Curie–Weiss type law with negative paramagnetic Curie temperature. The magnetic data also allow the estimation of NV4+ / Ntotal ratio.

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