Structural and spectroscopic investigation of the charge-ordered, short-range ordered, and disordered phases of the Co3O2BO3 ludwigite
Autor(a) principal: | |
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Data de Publicação: | 2021 |
Outros Autores: | , , , , , , , , , , , , , , |
Tipo de documento: | Artigo |
Idioma: | eng |
Título da fonte: | Repositório Institucional da UFRGS |
Texto Completo: | http://hdl.handle.net/10183/236834 |
Resumo: | Charge ordering is prone to occur in crystalline materials with mixed-valence ions. It is presumably accompanied by a structural phase transition, with possible exceptions in compounds that already present more than one inequivalent site for the mixed-valence ions in the charge-disordered phase. In this work, we investigate the representative case of the homometallic Co ludwigite Co2+2Co3+O2BO3 (Pbam space group) with four distinct Co crystallographic sites [M1–M4] surrounded by oxygen octahedra. The mixed-valent character of the Co ions up to at least T=873 K is verified through x-ray absorption near-edge structure (XANES) experiments. Single crystal x-ray diffraction (XRD) and neutron powder diffraction (NPD) confirm that the Co ions at the M4 site are much smaller than the others at low temperatures, consistent with a Co3+ oxidation state at M4 and Co2+ at the remaining sites. The size difference between the Co ions in the M4 and M2 sites is continuously reduced upon warming above ≈370 K, indicating a gradual charge redistribution within the M4−M2−M4 (424) ladder in the average structure. Minor structural anomalies with no space group modification are observed near 475 and 495 K, where sharp phase transitions were previously revealed by calorimetry and electrical resistivity data. An increasing structural disorder, beyond a conventional thermal effect, is noted above ≈370 K, manifested by an anomalous increment of XRD Debye-Waller factors and broadened vibrational modes observed by Raman scattering. The local Co-O distance distribution, revealed by Co K-edge extended x-ray absorption fine structure (EXAFS) data and analyzed with an evolutionary algorithm method, is similar to that inferred from the XRD crystal structure below ≈370 K. At higher temperatures, the local Co-O distance distribution remains similar to that found at low temperatures, at variance with the average crystal structure obtained with XRD. We conclude that the oxidation states Co2+ and Co3+ are instantaneously well defined in a local atomic level at all temperatures, however the thermal energy promotes local defects in the charge-ordered configuration of the 424 ladders upon warming. These defects coalesce into a phase-segregated state within a narrow temperature interval (475<T<495 K). Finally, a transition at ≈500 K revealed by differential scanning calorimetry (DSC) in the iron ludwigite Fe3O2BO3 is discussed. |
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Galdino, Carlos WilliamFreitas, DanieleMedrano, Cynthia Paola ContrerasSánchez, D. R.Souza, Rodolfo TartagliaRabello, L. P.Mendonça, Alberto AguiarGhivelder, LuisContinentino, Mucio AmadoZapata, Maximiliano Jesús MorenoPinheiro, Carlos BasílioAzevedo, Gustavo de MedeirosRodríguez-Velamazán, J. A.Garbarino, GastonNúñez-Regueiro, M.D.Granado, E.2022-04-07T04:49:44Z20211098-0121http://hdl.handle.net/10183/236834001137268Charge ordering is prone to occur in crystalline materials with mixed-valence ions. It is presumably accompanied by a structural phase transition, with possible exceptions in compounds that already present more than one inequivalent site for the mixed-valence ions in the charge-disordered phase. In this work, we investigate the representative case of the homometallic Co ludwigite Co2+2Co3+O2BO3 (Pbam space group) with four distinct Co crystallographic sites [M1–M4] surrounded by oxygen octahedra. The mixed-valent character of the Co ions up to at least T=873 K is verified through x-ray absorption near-edge structure (XANES) experiments. Single crystal x-ray diffraction (XRD) and neutron powder diffraction (NPD) confirm that the Co ions at the M4 site are much smaller than the others at low temperatures, consistent with a Co3+ oxidation state at M4 and Co2+ at the remaining sites. The size difference between the Co ions in the M4 and M2 sites is continuously reduced upon warming above ≈370 K, indicating a gradual charge redistribution within the M4−M2−M4 (424) ladder in the average structure. Minor structural anomalies with no space group modification are observed near 475 and 495 K, where sharp phase transitions were previously revealed by calorimetry and electrical resistivity data. An increasing structural disorder, beyond a conventional thermal effect, is noted above ≈370 K, manifested by an anomalous increment of XRD Debye-Waller factors and broadened vibrational modes observed by Raman scattering. The local Co-O distance distribution, revealed by Co K-edge extended x-ray absorption fine structure (EXAFS) data and analyzed with an evolutionary algorithm method, is similar to that inferred from the XRD crystal structure below ≈370 K. At higher temperatures, the local Co-O distance distribution remains similar to that found at low temperatures, at variance with the average crystal structure obtained with XRD. We conclude that the oxidation states Co2+ and Co3+ are instantaneously well defined in a local atomic level at all temperatures, however the thermal energy promotes local defects in the charge-ordered configuration of the 424 ladders upon warming. These defects coalesce into a phase-segregated state within a narrow temperature interval (475<T<495 K). Finally, a transition at ≈500 K revealed by differential scanning calorimetry (DSC) in the iron ludwigite Fe3O2BO3 is discussed.application/pdfengPhysical review. B, Condensed matter and materials physics. Woodbury. Vol. 104, no. 19 (Nov. 2021), 195151, 12 p.Transformações de faseCompostos de cobaltoDifração de raios XEstrutura fina estendida de absorção de raios x (EXAFS)Difração de nêutronsEspectroscopia de absorção de raios X próxima à bordaStructural and spectroscopic investigation of the charge-ordered, short-range ordered, and disordered phases of the Co3O2BO3 ludwigiteEstrangeiroinfo: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:UFRGSTEXT001137268.pdf.txt001137268.pdf.txtExtracted Texttext/plain54716http://www.lume.ufrgs.br/bitstream/10183/236834/2/001137268.pdf.txt939450788e517687dc9935a4b223e697MD52ORIGINAL001137268.pdfTexto completo (inglês)application/pdf1434466http://www.lume.ufrgs.br/bitstream/10183/236834/1/001137268.pdf4392c2fb7cde6e192bb64a2c76d7eb8dMD5110183/2368342022-04-20 04:56:03.507281oai:www.lume.ufrgs.br:10183/236834Repositório de PublicaçõesPUBhttps://lume.ufrgs.br/oai/requestopendoar:2022-04-20T07:56:03Repositório Institucional da UFRGS - Universidade Federal do Rio Grande do Sul (UFRGS)false |
dc.title.pt_BR.fl_str_mv |
Structural and spectroscopic investigation of the charge-ordered, short-range ordered, and disordered phases of the Co3O2BO3 ludwigite |
title |
Structural and spectroscopic investigation of the charge-ordered, short-range ordered, and disordered phases of the Co3O2BO3 ludwigite |
spellingShingle |
Structural and spectroscopic investigation of the charge-ordered, short-range ordered, and disordered phases of the Co3O2BO3 ludwigite Galdino, Carlos William Transformações de fase Compostos de cobalto Difração de raios X Estrutura fina estendida de absorção de raios x (EXAFS) Difração de nêutrons Espectroscopia de absorção de raios X próxima à borda |
title_short |
Structural and spectroscopic investigation of the charge-ordered, short-range ordered, and disordered phases of the Co3O2BO3 ludwigite |
title_full |
Structural and spectroscopic investigation of the charge-ordered, short-range ordered, and disordered phases of the Co3O2BO3 ludwigite |
title_fullStr |
Structural and spectroscopic investigation of the charge-ordered, short-range ordered, and disordered phases of the Co3O2BO3 ludwigite |
title_full_unstemmed |
Structural and spectroscopic investigation of the charge-ordered, short-range ordered, and disordered phases of the Co3O2BO3 ludwigite |
title_sort |
Structural and spectroscopic investigation of the charge-ordered, short-range ordered, and disordered phases of the Co3O2BO3 ludwigite |
author |
Galdino, Carlos William |
author_facet |
Galdino, Carlos William Freitas, Daniele Medrano, Cynthia Paola Contreras Sánchez, D. R. Souza, Rodolfo Tartaglia Rabello, L. P. Mendonça, Alberto Aguiar Ghivelder, Luis Continentino, Mucio Amado Zapata, Maximiliano Jesús Moreno Pinheiro, Carlos Basílio Azevedo, Gustavo de Medeiros Rodríguez-Velamazán, J. A. Garbarino, Gaston Núñez-Regueiro, M.D. Granado, E. |
author_role |
author |
author2 |
Freitas, Daniele Medrano, Cynthia Paola Contreras Sánchez, D. R. Souza, Rodolfo Tartaglia Rabello, L. P. Mendonça, Alberto Aguiar Ghivelder, Luis Continentino, Mucio Amado Zapata, Maximiliano Jesús Moreno Pinheiro, Carlos Basílio Azevedo, Gustavo de Medeiros Rodríguez-Velamazán, J. A. Garbarino, Gaston Núñez-Regueiro, M.D. Granado, E. |
author2_role |
author author author author author author author author author author author author author author author |
dc.contributor.author.fl_str_mv |
Galdino, Carlos William Freitas, Daniele Medrano, Cynthia Paola Contreras Sánchez, D. R. Souza, Rodolfo Tartaglia Rabello, L. P. Mendonça, Alberto Aguiar Ghivelder, Luis Continentino, Mucio Amado Zapata, Maximiliano Jesús Moreno Pinheiro, Carlos Basílio Azevedo, Gustavo de Medeiros Rodríguez-Velamazán, J. A. Garbarino, Gaston Núñez-Regueiro, M.D. Granado, E. |
dc.subject.por.fl_str_mv |
Transformações de fase Compostos de cobalto Difração de raios X Estrutura fina estendida de absorção de raios x (EXAFS) Difração de nêutrons Espectroscopia de absorção de raios X próxima à borda |
topic |
Transformações de fase Compostos de cobalto Difração de raios X Estrutura fina estendida de absorção de raios x (EXAFS) Difração de nêutrons Espectroscopia de absorção de raios X próxima à borda |
description |
Charge ordering is prone to occur in crystalline materials with mixed-valence ions. It is presumably accompanied by a structural phase transition, with possible exceptions in compounds that already present more than one inequivalent site for the mixed-valence ions in the charge-disordered phase. In this work, we investigate the representative case of the homometallic Co ludwigite Co2+2Co3+O2BO3 (Pbam space group) with four distinct Co crystallographic sites [M1–M4] surrounded by oxygen octahedra. The mixed-valent character of the Co ions up to at least T=873 K is verified through x-ray absorption near-edge structure (XANES) experiments. Single crystal x-ray diffraction (XRD) and neutron powder diffraction (NPD) confirm that the Co ions at the M4 site are much smaller than the others at low temperatures, consistent with a Co3+ oxidation state at M4 and Co2+ at the remaining sites. The size difference between the Co ions in the M4 and M2 sites is continuously reduced upon warming above ≈370 K, indicating a gradual charge redistribution within the M4−M2−M4 (424) ladder in the average structure. Minor structural anomalies with no space group modification are observed near 475 and 495 K, where sharp phase transitions were previously revealed by calorimetry and electrical resistivity data. An increasing structural disorder, beyond a conventional thermal effect, is noted above ≈370 K, manifested by an anomalous increment of XRD Debye-Waller factors and broadened vibrational modes observed by Raman scattering. The local Co-O distance distribution, revealed by Co K-edge extended x-ray absorption fine structure (EXAFS) data and analyzed with an evolutionary algorithm method, is similar to that inferred from the XRD crystal structure below ≈370 K. At higher temperatures, the local Co-O distance distribution remains similar to that found at low temperatures, at variance with the average crystal structure obtained with XRD. We conclude that the oxidation states Co2+ and Co3+ are instantaneously well defined in a local atomic level at all temperatures, however the thermal energy promotes local defects in the charge-ordered configuration of the 424 ladders upon warming. These defects coalesce into a phase-segregated state within a narrow temperature interval (475<T<495 K). Finally, a transition at ≈500 K revealed by differential scanning calorimetry (DSC) in the iron ludwigite Fe3O2BO3 is discussed. |
publishDate |
2021 |
dc.date.issued.fl_str_mv |
2021 |
dc.date.accessioned.fl_str_mv |
2022-04-07T04:49:44Z |
dc.type.driver.fl_str_mv |
Estrangeiro info:eu-repo/semantics/article |
dc.type.status.fl_str_mv |
info:eu-repo/semantics/publishedVersion |
format |
article |
status_str |
publishedVersion |
dc.identifier.uri.fl_str_mv |
http://hdl.handle.net/10183/236834 |
dc.identifier.issn.pt_BR.fl_str_mv |
1098-0121 |
dc.identifier.nrb.pt_BR.fl_str_mv |
001137268 |
identifier_str_mv |
1098-0121 001137268 |
url |
http://hdl.handle.net/10183/236834 |
dc.language.iso.fl_str_mv |
eng |
language |
eng |
dc.relation.ispartof.pt_BR.fl_str_mv |
Physical review. B, Condensed matter and materials physics. Woodbury. Vol. 104, no. 19 (Nov. 2021), 195151, 12 p. |
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info:eu-repo/semantics/openAccess |
eu_rights_str_mv |
openAccess |
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