Produção e estudo dos defeitos de materiais fotossensíveis com estrutura cristalina do tipo silenita

Detalhes bibliográficos
Autor(a) principal: Santos, Denise de Jesus
Data de Publicação: 2014
Tipo de documento: Tese
Idioma: por
Título da fonte: Repositório Institucional da UFS
Texto Completo: https://ri.ufs.br/handle/riufs/5317
Resumo: Photorefractive BTO presents useful properties for applications such as real-time holography, coherent light amplification and optical information processing, among others. The performance strongly depends on the defects induced by impurities, which can act as charge donors or acceptors. Defects can also be created by doping so that the properties can be adjusted to the desired application. Since ceramic reproduce well the single crystal properties and have advantages such as the simplicity and low cost of processing, they become suitable for the study of the relationship between properties and defects in this material. The subject of this work was the production and characterization of bismuth titanate ceramics ( Bi12TiO20 - BTO) pure and doped with transition metals and rare earths. The study was focused on the point defects related to the site occupancy of the dopant in the BTO matrix, as well as on the valence of the dopant and possible charge compensation mechanisms associated with the defects. In this work, BTO ceramics were produced by solid state synthesis with calcination at 700º C/6h and sintering at 800º C/3h. The characterization techniques employed were Xray Diffraction (XRD), X-ray absorption spectroscopy (XAS), Scanning Electron Microscopy (SEM) and Impedance Spectroscopy (IS). Undoped and Dy , Er , Eu, Cr and Mn-doped BTO ceramic powders were produced, as well as ceramic bodies undoped and doped with Dy, Cr and Mn. All samples presented single phase Bi12TiO20. The XAS analysis revealed the presence of T4+ and metallic Ti in BTO, a result that adds detail to the model for the formation of intrinsic defects in this material. Transition metals Cr and Mn presented oxidation states 6+ and 4+, respectively, when inserted into the BTO matrix, while the other elements present valence 3+. Concerning the site occupancy, it was determined that the Dy tends to occupy the Bi3+ site, while Er, Eu, Mn and Cr tend to occupy the Ti4+ site. Impedance measurements showed that none of the doped samples had higher dark conductivity than pure sample. For the samples doped with Mn and Dy, which tend to occupy the Ti and Bi sites, respectively, the charge transport mechanisms are exactly the same as those verified in pure sample. For the Cr-doped sample, the Ti substitution occurs with a charge compensation mechanism that possibly give rise to new defects in the material.
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spelling Santos, Denise de JesusMacedo, Zélia Soareshttp://lattes.cnpq.br/04397618057261272017-09-26T18:27:22Z2017-09-26T18:27:22Z2014-03-28https://ri.ufs.br/handle/riufs/5317Photorefractive BTO presents useful properties for applications such as real-time holography, coherent light amplification and optical information processing, among others. The performance strongly depends on the defects induced by impurities, which can act as charge donors or acceptors. Defects can also be created by doping so that the properties can be adjusted to the desired application. Since ceramic reproduce well the single crystal properties and have advantages such as the simplicity and low cost of processing, they become suitable for the study of the relationship between properties and defects in this material. The subject of this work was the production and characterization of bismuth titanate ceramics ( Bi12TiO20 - BTO) pure and doped with transition metals and rare earths. The study was focused on the point defects related to the site occupancy of the dopant in the BTO matrix, as well as on the valence of the dopant and possible charge compensation mechanisms associated with the defects. In this work, BTO ceramics were produced by solid state synthesis with calcination at 700º C/6h and sintering at 800º C/3h. The characterization techniques employed were Xray Diffraction (XRD), X-ray absorption spectroscopy (XAS), Scanning Electron Microscopy (SEM) and Impedance Spectroscopy (IS). Undoped and Dy , Er , Eu, Cr and Mn-doped BTO ceramic powders were produced, as well as ceramic bodies undoped and doped with Dy, Cr and Mn. All samples presented single phase Bi12TiO20. The XAS analysis revealed the presence of T4+ and metallic Ti in BTO, a result that adds detail to the model for the formation of intrinsic defects in this material. Transition metals Cr and Mn presented oxidation states 6+ and 4+, respectively, when inserted into the BTO matrix, while the other elements present valence 3+. Concerning the site occupancy, it was determined that the Dy tends to occupy the Bi3+ site, while Er, Eu, Mn and Cr tend to occupy the Ti4+ site. Impedance measurements showed that none of the doped samples had higher dark conductivity than pure sample. For the samples doped with Mn and Dy, which tend to occupy the Ti and Bi sites, respectively, the charge transport mechanisms are exactly the same as those verified in pure sample. For the Cr-doped sample, the Ti substitution occurs with a charge compensation mechanism that possibly give rise to new defects in the material.O BTO possui propriedades fotorrefrativas de interesse para aplicações como a holografia em tempo real, a amplificação de luz coerente e processamento de informação óptica, entre outras. O desempenho dos cristais fotorrefrativos depende fortemente dos defeitos criados por impurezas, os quais podem atuar como doadores ou aceitadores de carga. Os defeitos também podem ser inseridos por dopagem a fim de que as propriedades sejam adaptadas ao objetivo desejado. Uma vez que cerâmicas reproduzem bem as características do monocristal e apresentam vantagens de produção em relação aos materiais monocristalinos, como facilidade e baixo custo de processamento, elas se tornam adequadas ao estudo da relação entre defeitos e propriedades neste material. O objetivo deste trabalho foi a produção e caracterização de cerâmicas de Titanato de Bismuto (Bi12TiO20 - BTO) puro e dopado com metais de transição e terras raras, visando o estudo dos defeitos pontuais relacionados com e sitio de ocupação do dopante na matriz do BTO, valência do íon dopante incorporado na matriz cristalina e possíveis mecanismos de compensação de carga associados aos defeitos. Neste trabalho, cerâmicas de BTO foram produzidas por síntese de estado sólido, com calcinação a 700º C/6h, seguida de sinterização a 800º C/3h. Utilizamos como principais técnicas de caracterização a Difratometria de Raios X (DRX), Espectroscopia de Absorção de Raios X (XAS), Microscopia Eletrônica de Varredura (MEV) e Espectroscopia de Impedância (IS). Foram produzidos pós cerâmicos puros e dopados com Dy, Er, Eu, Cr e Mn e corpos cerâmicos de BTO puros e dopados com Dy, Cr e Mn. Todas as amostras apresentaram a fase Bi12TiO20. As análises de XAS mostraram a presença de Ti4+ e Ti metálico no BTO, resultado que acrescenta detalhes ao modelo de formação do defeito intrínseco neste material. Os metais de transição Cr e Mn apresentaram estados de oxidação 6+ e 4+, respectivamente, quando inseridos na matriz de BTO, enquanto os outros elementos apresentaram valência 3+. Em relação ao sítio ocupado pelos íons dopantes, determinou-se que o Dy tende a ocupar o sítio do Bi3+, enquanto o Er, Eu, Cr e Mn tendem a ocupar o sítio do Ti4+. As medidas de impedância mostraram que nenhuma das amostras dopadas apresentou maior condutividade no escuro do que a amostra pura. Nas amostras dopadas com Mn e Dy que ocupam o sitio do Ti e Bi, espectivamente os mecanismos de transporte de carga são exatamente iguais ao da amostra pura. Na amostra dopada com Cr, ao substituir o sitio do Ti ocorrem mecanismos de compensação de carga que dão origem a novos defeitos no material.application/pdfporFísico-químicaCristalografiaTitanatosBismutoMetais de transiçãoTerras-rarasDifraçãoRaios XMateriais fotossensíveisChemistry, Physical and theoreticalCrystallographyDifrationEarths, RareTitanatesTransition metalsX-raysCNPQ::CIENCIAS EXATAS E DA TERRA::FISICAProdução e estudo dos defeitos de materiais fotossensíveis com estrutura cristalina do tipo silenitainfo:eu-repo/semantics/publishedVersioninfo:eu-repo/semantics/doctoralThesisPós-Graduação em Físicainfo:eu-repo/semantics/openAccessreponame:Repositório Institucional da UFSinstname:Universidade Federal de Sergipe (UFS)instacron:UFSORIGINALDENISE_JESUS_SANTOS.pdfapplication/pdf8802701https://ri.ufs.br/jspui/bitstream/riufs/5317/1/DENISE_JESUS_SANTOS.pdf86eacade8884f24dae901831244788d1MD51TEXTDENISE_JESUS_SANTOS.pdf.txtDENISE_JESUS_SANTOS.pdf.txtExtracted texttext/plain175857https://ri.ufs.br/jspui/bitstream/riufs/5317/2/DENISE_JESUS_SANTOS.pdf.txtffcf148516d6cf7c950b32a6524c688bMD52THUMBNAILDENISE_JESUS_SANTOS.pdf.jpgDENISE_JESUS_SANTOS.pdf.jpgGenerated Thumbnailimage/jpeg1269https://ri.ufs.br/jspui/bitstream/riufs/5317/3/DENISE_JESUS_SANTOS.pdf.jpg4a1f9d0abcd253d54b1a3cef607a81d2MD53riufs/53172019-07-30 19:22:28.616oai:ufs.br:riufs/5317Repositório InstitucionalPUBhttps://ri.ufs.br/oai/requestrepositorio@academico.ufs.bropendoar:2019-07-30T22:22:28Repositório Institucional da UFS - Universidade Federal de Sergipe (UFS)false
dc.title.por.fl_str_mv Produção e estudo dos defeitos de materiais fotossensíveis com estrutura cristalina do tipo silenita
title Produção e estudo dos defeitos de materiais fotossensíveis com estrutura cristalina do tipo silenita
spellingShingle Produção e estudo dos defeitos de materiais fotossensíveis com estrutura cristalina do tipo silenita
Santos, Denise de Jesus
Físico-química
Cristalografia
Titanatos
Bismuto
Metais de transição
Terras-raras
Difração
Raios X
Materiais fotossensíveis
Chemistry, Physical and theoretical
Crystallography
Difration
Earths, Rare
Titanates
Transition metals
X-rays
CNPQ::CIENCIAS EXATAS E DA TERRA::FISICA
title_short Produção e estudo dos defeitos de materiais fotossensíveis com estrutura cristalina do tipo silenita
title_full Produção e estudo dos defeitos de materiais fotossensíveis com estrutura cristalina do tipo silenita
title_fullStr Produção e estudo dos defeitos de materiais fotossensíveis com estrutura cristalina do tipo silenita
title_full_unstemmed Produção e estudo dos defeitos de materiais fotossensíveis com estrutura cristalina do tipo silenita
title_sort Produção e estudo dos defeitos de materiais fotossensíveis com estrutura cristalina do tipo silenita
author Santos, Denise de Jesus
author_facet Santos, Denise de Jesus
author_role author
dc.contributor.author.fl_str_mv Santos, Denise de Jesus
dc.contributor.advisor1.fl_str_mv Macedo, Zélia Soares
dc.contributor.authorLattes.fl_str_mv http://lattes.cnpq.br/0439761805726127
contributor_str_mv Macedo, Zélia Soares
dc.subject.por.fl_str_mv Físico-química
Cristalografia
Titanatos
Bismuto
Metais de transição
Terras-raras
Difração
Raios X
Materiais fotossensíveis
topic Físico-química
Cristalografia
Titanatos
Bismuto
Metais de transição
Terras-raras
Difração
Raios X
Materiais fotossensíveis
Chemistry, Physical and theoretical
Crystallography
Difration
Earths, Rare
Titanates
Transition metals
X-rays
CNPQ::CIENCIAS EXATAS E DA TERRA::FISICA
dc.subject.eng.fl_str_mv Chemistry, Physical and theoretical
Crystallography
Difration
Earths, Rare
Titanates
Transition metals
X-rays
dc.subject.cnpq.fl_str_mv CNPQ::CIENCIAS EXATAS E DA TERRA::FISICA
description Photorefractive BTO presents useful properties for applications such as real-time holography, coherent light amplification and optical information processing, among others. The performance strongly depends on the defects induced by impurities, which can act as charge donors or acceptors. Defects can also be created by doping so that the properties can be adjusted to the desired application. Since ceramic reproduce well the single crystal properties and have advantages such as the simplicity and low cost of processing, they become suitable for the study of the relationship between properties and defects in this material. The subject of this work was the production and characterization of bismuth titanate ceramics ( Bi12TiO20 - BTO) pure and doped with transition metals and rare earths. The study was focused on the point defects related to the site occupancy of the dopant in the BTO matrix, as well as on the valence of the dopant and possible charge compensation mechanisms associated with the defects. In this work, BTO ceramics were produced by solid state synthesis with calcination at 700º C/6h and sintering at 800º C/3h. The characterization techniques employed were Xray Diffraction (XRD), X-ray absorption spectroscopy (XAS), Scanning Electron Microscopy (SEM) and Impedance Spectroscopy (IS). Undoped and Dy , Er , Eu, Cr and Mn-doped BTO ceramic powders were produced, as well as ceramic bodies undoped and doped with Dy, Cr and Mn. All samples presented single phase Bi12TiO20. The XAS analysis revealed the presence of T4+ and metallic Ti in BTO, a result that adds detail to the model for the formation of intrinsic defects in this material. Transition metals Cr and Mn presented oxidation states 6+ and 4+, respectively, when inserted into the BTO matrix, while the other elements present valence 3+. Concerning the site occupancy, it was determined that the Dy tends to occupy the Bi3+ site, while Er, Eu, Mn and Cr tend to occupy the Ti4+ site. Impedance measurements showed that none of the doped samples had higher dark conductivity than pure sample. For the samples doped with Mn and Dy, which tend to occupy the Ti and Bi sites, respectively, the charge transport mechanisms are exactly the same as those verified in pure sample. For the Cr-doped sample, the Ti substitution occurs with a charge compensation mechanism that possibly give rise to new defects in the material.
publishDate 2014
dc.date.issued.fl_str_mv 2014-03-28
dc.date.accessioned.fl_str_mv 2017-09-26T18:27:22Z
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