High temperature emissivity, reflectivity, and x-ray absorption of BiFeO3

Detalhes bibliográficos
Autor(a) principal: Massa, Néstor E.
Data de Publicação: 2010
Outros Autores: Del Campo, Leire, Meneses, Domingos de Souza, Echegut, Patrick, Fabbris, Gilberto Fernandes Lopes, Azevedo, Gustavo de Medeiros, Martínez Lope, María Jesús, Alonso, José Antônio
Tipo de documento: Artigo
Idioma: eng
Título da fonte: Repositório Institucional da UFRGS
Texto Completo: http://hdl.handle.net/10183/96281
Resumo: We report on the lattice evolution of BiFeO3 as function of temperature using far infrared emissivity, reflectivity, and x-ray absorption local structure. A power law fit to the lowest frequency soft phonon in the magnetic ordered phase yields an exponent β=0.25 as for a tricritical point. At about 200 K below TN~640 K it ceases softening as consequence of BiFeO3 metastability. We identified this temperature as corresponding to a crossover transition to an order-disorder regime. Above~700 K strong band overlapping, merging, and smearing of modes are consequence of thermal fluctuations and chemical disorder. Vibrational modes show band splits in the ferroelectric phase as emerging from triple degenerated species as from a paraelectric cubic phase above TC~1090 K. Temperature dependent x-ray absorption near edge structure XANES at the Fe K edge shows that lower temperature Fe3+ turns into Fe2+. While this matches the FeO wüstite XANES profile, the Bi LIII-edge downshift suggests a high temperature very complex bond configuration at the distorted A perovskite site. Overall, our local structural measurements reveal high temperature defect-induced irreversible lattice changes, below, and above the ferroelectric transition, in an environment lacking of long-range coherence. We did not find an insulator to metal transition prior to melting.
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spelling Massa, Néstor E.Del Campo, LeireMeneses, Domingos de SouzaEchegut, PatrickFabbris, Gilberto Fernandes LopesAzevedo, Gustavo de MedeirosMartínez Lope, María JesúsAlonso, José Antônio2014-06-10T02:05:14Z20100021-8979http://hdl.handle.net/10183/96281000767131We report on the lattice evolution of BiFeO3 as function of temperature using far infrared emissivity, reflectivity, and x-ray absorption local structure. A power law fit to the lowest frequency soft phonon in the magnetic ordered phase yields an exponent β=0.25 as for a tricritical point. At about 200 K below TN~640 K it ceases softening as consequence of BiFeO3 metastability. We identified this temperature as corresponding to a crossover transition to an order-disorder regime. Above~700 K strong band overlapping, merging, and smearing of modes are consequence of thermal fluctuations and chemical disorder. Vibrational modes show band splits in the ferroelectric phase as emerging from triple degenerated species as from a paraelectric cubic phase above TC~1090 K. Temperature dependent x-ray absorption near edge structure XANES at the Fe K edge shows that lower temperature Fe3+ turns into Fe2+. While this matches the FeO wüstite XANES profile, the Bi LIII-edge downshift suggests a high temperature very complex bond configuration at the distorted A perovskite site. Overall, our local structural measurements reveal high temperature defect-induced irreversible lattice changes, below, and above the ferroelectric transition, in an environment lacking of long-range coherence. We did not find an insulator to metal transition prior to melting.application/pdfengJournal of applied physics. Melville. Vol. 108, no. 8 (Oct. 2010), 084114, 8 p.Física da matéria condensadaCompostos de bismutoFlutuações críticasPontos criticosEmissividadeTransições ferroelétricasTransformações displacivasFononsReflexibilidadeXanesHigh temperature emissivity, reflectivity, and x-ray absorption of BiFeO3Estrangeiroinfo:eu-repo/semantics/articleinfo:eu-repo/semantics/publishedVersioninfo:eu-repo/semantics/openAccessreponame:Repositório Institucional da UFRGSinstname:Universidade Federal do Rio Grande do Sul (UFRGS)instacron:UFRGSORIGINAL000767131.pdf000767131.pdfTexto completo (inglês)application/pdf1670853http://www.lume.ufrgs.br/bitstream/10183/96281/1/000767131.pdf34757fd6130a91e124b46a675e204884MD51TEXT000767131.pdf.txt000767131.pdf.txtExtracted Texttext/plain43687http://www.lume.ufrgs.br/bitstream/10183/96281/2/000767131.pdf.txt09947e5953695e335871ada4f5581cacMD52THUMBNAIL000767131.pdf.jpg000767131.pdf.jpgGenerated Thumbnailimage/jpeg1589http://www.lume.ufrgs.br/bitstream/10183/96281/3/000767131.pdf.jpga3979a5191e3faae7ac77c4e52aaecb6MD5310183/962812018-10-18 08:03:51.158oai:www.lume.ufrgs.br:10183/96281Repositório de PublicaçõesPUBhttps://lume.ufrgs.br/oai/requestopendoar:2018-10-18T11:03:51Repositório Institucional da UFRGS - Universidade Federal do Rio Grande do Sul (UFRGS)false
dc.title.pt_BR.fl_str_mv High temperature emissivity, reflectivity, and x-ray absorption of BiFeO3
title High temperature emissivity, reflectivity, and x-ray absorption of BiFeO3
spellingShingle High temperature emissivity, reflectivity, and x-ray absorption of BiFeO3
Massa, Néstor E.
Física da matéria condensada
Compostos de bismuto
Flutuações críticas
Pontos criticos
Emissividade
Transições ferroelétricas
Transformações displacivas
Fonons
Reflexibilidade
Xanes
title_short High temperature emissivity, reflectivity, and x-ray absorption of BiFeO3
title_full High temperature emissivity, reflectivity, and x-ray absorption of BiFeO3
title_fullStr High temperature emissivity, reflectivity, and x-ray absorption of BiFeO3
title_full_unstemmed High temperature emissivity, reflectivity, and x-ray absorption of BiFeO3
title_sort High temperature emissivity, reflectivity, and x-ray absorption of BiFeO3
author Massa, Néstor E.
author_facet Massa, Néstor E.
Del Campo, Leire
Meneses, Domingos de Souza
Echegut, Patrick
Fabbris, Gilberto Fernandes Lopes
Azevedo, Gustavo de Medeiros
Martínez Lope, María Jesús
Alonso, José Antônio
author_role author
author2 Del Campo, Leire
Meneses, Domingos de Souza
Echegut, Patrick
Fabbris, Gilberto Fernandes Lopes
Azevedo, Gustavo de Medeiros
Martínez Lope, María Jesús
Alonso, José Antônio
author2_role author
author
author
author
author
author
author
dc.contributor.author.fl_str_mv Massa, Néstor E.
Del Campo, Leire
Meneses, Domingos de Souza
Echegut, Patrick
Fabbris, Gilberto Fernandes Lopes
Azevedo, Gustavo de Medeiros
Martínez Lope, María Jesús
Alonso, José Antônio
dc.subject.por.fl_str_mv Física da matéria condensada
Compostos de bismuto
Flutuações críticas
Pontos criticos
Emissividade
Transições ferroelétricas
Transformações displacivas
Fonons
Reflexibilidade
Xanes
topic Física da matéria condensada
Compostos de bismuto
Flutuações críticas
Pontos criticos
Emissividade
Transições ferroelétricas
Transformações displacivas
Fonons
Reflexibilidade
Xanes
description We report on the lattice evolution of BiFeO3 as function of temperature using far infrared emissivity, reflectivity, and x-ray absorption local structure. A power law fit to the lowest frequency soft phonon in the magnetic ordered phase yields an exponent β=0.25 as for a tricritical point. At about 200 K below TN~640 K it ceases softening as consequence of BiFeO3 metastability. We identified this temperature as corresponding to a crossover transition to an order-disorder regime. Above~700 K strong band overlapping, merging, and smearing of modes are consequence of thermal fluctuations and chemical disorder. Vibrational modes show band splits in the ferroelectric phase as emerging from triple degenerated species as from a paraelectric cubic phase above TC~1090 K. Temperature dependent x-ray absorption near edge structure XANES at the Fe K edge shows that lower temperature Fe3+ turns into Fe2+. While this matches the FeO wüstite XANES profile, the Bi LIII-edge downshift suggests a high temperature very complex bond configuration at the distorted A perovskite site. Overall, our local structural measurements reveal high temperature defect-induced irreversible lattice changes, below, and above the ferroelectric transition, in an environment lacking of long-range coherence. We did not find an insulator to metal transition prior to melting.
publishDate 2010
dc.date.issued.fl_str_mv 2010
dc.date.accessioned.fl_str_mv 2014-06-10T02:05:14Z
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dc.identifier.issn.pt_BR.fl_str_mv 0021-8979
dc.identifier.nrb.pt_BR.fl_str_mv 000767131
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dc.language.iso.fl_str_mv eng
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dc.relation.ispartof.pt_BR.fl_str_mv Journal of applied physics. Melville. Vol. 108, no. 8 (Oct. 2010), 084114, 8 p.
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