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Title: Experimental and Calculated Ti K-Edge XANES Spectra of Pb1-xLaxTiO3 Ferroelectric Ceramic Compounds

Abstract

The X-ray absorption near-edge structures (XANES) at the Ti K-edge of Pb1-xLaxTiO3 ferroelectric ceramic compounds are analyzed as a function of the sample composition. The calculated XANES spectra using the FEFF8.2 code are compared with experimental data. Experimental results show that the local distortion around Ti atoms has different composition dependence as compared to the crystallographic structure. Moreover, this distortion is also observed in samples presenting a crystallographically cubic phase. The agreement between experimental XANES spectra and theoretical ones deduced from the XRD results was good only for undoped and weakly doped samples. The use of structural models based on the XRD technique for samples containing higher amounts of lanthanum is not appropriate to describe correctly the local order around Ti atoms in this system.

Authors:
;  [1];  [2];  [3]
  1. Intituto de Fisica de Sao Carlos, Universidade de Sao Paulo, C. P. 369, 13560-970, Sao Carlos, SP (Brazil)
  2. Laboratoire de Physique Structurale des Molecules et Materiaux, Universite Paris XII - Creteil Cedex (France)
  3. Departamento de Fisica, Universidade Federal de Sao Carlos, Sao Carlos - SP (Brazil)
Publication Date:
OSTI Identifier:
21054664
Resource Type:
Journal Article
Resource Relation:
Journal Name: AIP Conference Proceedings; Journal Volume: 882; Journal Issue: 1; Conference: XAFS13: 13. international conference on X-ray absorption fine structure, Stanford, CA (United States), 9-14 Jul 2006; Other Information: DOI: 10.1063/1.2644571; (c) 2007 American Institute of Physics; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; ABSORPTION SPECTRA; ABSORPTION SPECTROSCOPY; ATOMS; CERAMICS; CRYSTAL STRUCTURE; DOPED MATERIALS; FERROELECTRIC MATERIALS; LANTHANUM; LANTHANUM COMPOUNDS; LEAD COMPOUNDS; TITANATES; X-RAY DIFFRACTION; X-RAY SPECTRA; X-RAY SPECTROSCOPY

Citation Formats

Mastelaro, V. R., Neves, P. P., Michalowicz, A., and Eiras, J. A.. Experimental and Calculated Ti K-Edge XANES Spectra of Pb1-xLaxTiO3 Ferroelectric Ceramic Compounds. United States: N. p., 2007. Web. doi:10.1063/1.2644571.
Mastelaro, V. R., Neves, P. P., Michalowicz, A., & Eiras, J. A.. Experimental and Calculated Ti K-Edge XANES Spectra of Pb1-xLaxTiO3 Ferroelectric Ceramic Compounds. United States. doi:10.1063/1.2644571.
Mastelaro, V. R., Neves, P. P., Michalowicz, A., and Eiras, J. A.. Fri . "Experimental and Calculated Ti K-Edge XANES Spectra of Pb1-xLaxTiO3 Ferroelectric Ceramic Compounds". United States. doi:10.1063/1.2644571.
@article{osti_21054664,
title = {Experimental and Calculated Ti K-Edge XANES Spectra of Pb1-xLaxTiO3 Ferroelectric Ceramic Compounds},
author = {Mastelaro, V. R. and Neves, P. P. and Michalowicz, A. and Eiras, J. A.},
abstractNote = {The X-ray absorption near-edge structures (XANES) at the Ti K-edge of Pb1-xLaxTiO3 ferroelectric ceramic compounds are analyzed as a function of the sample composition. The calculated XANES spectra using the FEFF8.2 code are compared with experimental data. Experimental results show that the local distortion around Ti atoms has different composition dependence as compared to the crystallographic structure. Moreover, this distortion is also observed in samples presenting a crystallographically cubic phase. The agreement between experimental XANES spectra and theoretical ones deduced from the XRD results was good only for undoped and weakly doped samples. The use of structural models based on the XRD technique for samples containing higher amounts of lanthanum is not appropriate to describe correctly the local order around Ti atoms in this system.},
doi = {10.1063/1.2644571},
journal = {AIP Conference Proceedings},
number = 1,
volume = 882,
place = {United States},
year = {Fri Feb 02 00:00:00 EST 2007},
month = {Fri Feb 02 00:00:00 EST 2007}
}
  • Experimental Ti K-edge x-ray-absorption near-edge structure (XANES) spectra for a variety of Ti(IV)-bearing crystalline oxide model compounds are compared with those calculated using the {ital ab initio} multiple-scattering code FEFF7. A scattering-theoretic interpretation of various features in the experimental spectra, including pre-edge and main-edge peaks, is presented together with an interpretation of the effects of disorder. The observed pre-edge features are found to vary in both position (by {approx}2{plus_minus}0.1eV) and normalized height (from {approx}0.04 to 1.0{plus_minus}0.05) as a function of Ti coordination (4, 5, or 6 oxygen nearest neighbors), in agreement with calculations. In aperiodic oxide compounds where the Timore » coordination is unknown (e.g., titanosilicate glasses and melts), pre-edge position and height can be used to derive reliable information on Ti coordination chemistry. For example, one can distinguish between fivefold coordinated Ti (i.e., TiO{sub 5}) and a 50:50 mixture of fourfold- and sixfold-coordinated Ti (i.e., TiO{sub 4} vs TiO{sub 6}). Finally, it is proposed that the intensity of the main-edge features can be used as a probe of disorder in the short- and medium-range environment of Ti. This is exemplified by Ti XANES studies of the effect of radiation damage on CaTiSiO{sub 5} and the melting of K{sub 2}TiSi{sub 2}O{sub 7} glass at high temperature. {copyright} {ital 1997} {ital The American Physical Society}« less
  • This work reports a theoretical study of the x-ray absorption near-edge structure spectra at the Cu K edge in several Cu(II) complexes with N-coordinating ligands showing a square-planar arrangement around metal cation. It is shown that single-channel multiple-scattering calculations are not able to reproduce the experimental spectra. The comparison between experimental data and ab initio computations indicates the need of including the contribution of two electronic configurations (3d{sup 9} and 3d{sup 10}L) to account for a proper description of the final state during the photoabsorption process. The best agreement between theory and experiment is obtained by considering a relative weightmore » of 68% and 32% for the two absorption channels 3d{sup 10}L and 3d{sup 9}, respectively.« less
  • Experimental Mg K-edge XANES spectra were obtained for crystals and synthetic glasses. To interpret the experiments, two different ab initio XANES calculation methods were employed. The first one is based on multiple-scattering calculations and muffin-tin potentials (FEFF package). The second uses a plane-wave basis set, norm-conserving pseudo-potentials, periodic boundary conditions. The resulting calculations for reference models with three different Mg coordinations are used to derive the best way to analyze the experimental XANES spectra for the glasses.
  • The pre-edge peaks of Ti K-edge XANES have been widely used in determining Ti coordination in amorphous materials and in crystals despite the fact that coordination is not the only factor that the pre-edge peaks depend on. This work thoroughly examines the dependence of the shape of Ti K pre-edge peaks on various geometrical parameters (coordination, symmetry, Ti-O bond length and bond angle) using distorted rutile TiO{sub 2} as models. We conclude that the greatest impact on the pre-edge peaks arises from a reduction in Ti-O bond length, although other parameters such as symmetry and coordination all have some effect.
  • The N K-edge X-ray absorption near edge structure (XANES) spectra of the purine-containing nucleotide, guanosine 5{sup ′}-monophosphate (GMP), in aqueous solution are measured under various pH conditions. The spectra show characteristic peaks, which originate from resonant excitations of N 1s electrons to π* orbitals inside the guanine moiety of GMP. The relative intensities of these peaks depend on the pH values of the solution. The pH dependence is explained by the core-level shift of N atoms at specific sites caused by protonation and deprotonation. The experimental spectra are compared with theoretical spectra calculated by using density functional theory for GMPmore » and the other purine-containing nucleotides, adenosine 5{sup ′}-monophosphate, and adenosine 5{sup ′}-triphosphate. The N K-edge XANES spectra for all of these nucleotides are classified by the numbers of N atoms with particular chemical bonding characteristics in the purine moiety.« less