Caracterização estrutural e óptica do composto NaYP2O7 dopado com terras raras
Autor(a) principal: | |
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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/5321 |
Resumo: | The aims of this work were to produce and investigate the properties of NaYP2O7 and NaY0.99Ln0.01P2O7 (Ln = Ce, Sm, Eu, Tb and Yb) polycrystalline samples. The synthesis was done via a modified sol-gel method using PVA as polymeric agent. In order to obtain single crystalline phase, it was necessary to use molar ratio Na:Y:P = 1.15:1:2, which is not the stoichiometric, with two calcination steps at 400 ºC / 4 h and 600 ºC / 4 h. Structural characterizations of the synthesized material were performed by X-ray Diffraction and Absorption (XRD and XAS). It was observed that the dopant ions were incorporated into the matrix without changing the structure. Under VUV excitation, the undoped sample presented a luminescent emission spectrum which was attributed to self-trapped exciton recombination. On the other hand, the photoluminescence (PL) of doped samples presented the emission lines characteristic of each dopant. From the photoluminescence excitation curves, 4f-5d transitions were identified for Ce3+, Sm3+ and Tb3+ doped samples and charge transfer processes were noticed for that of Eu3+, Sm3+ and Yb3+. The experimental data of PL was used to determine the positions of the energy levels of all lanthanides (with oxidation states of 3+ or 2+) relative to the valence and conduction bands of NaYP2O7. The model successfully provided the positions of electronic levels within the bandgap, with excellent agreement with the experimental spectra. Thermoluminescence (TL) glow curves were measured for co-doped samples NaYP2O7:Ce3+,Ln3+ (Ln = Dy, Ho and Sm) in order to investigate the nature of the trapping centres. The values determined for the activation energies were comparable with the position of dopant-induced electronic levels, whereas the frequency factor related to the TL peak of Ho-doped sample agreed with the phonon frequency for the lattice. The results indicate that the Ce3+ acts as recombination centre whereas the codopants create electron trap levels. |
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Novais, Suellen Maria ValerianoMacedo, Zélia Soareshttp://lattes.cnpq.br/42166323652104652017-09-26T18:27:24Z2017-09-26T18:27:24Z2014-02-18https://ri.ufs.br/handle/riufs/5321The aims of this work were to produce and investigate the properties of NaYP2O7 and NaY0.99Ln0.01P2O7 (Ln = Ce, Sm, Eu, Tb and Yb) polycrystalline samples. The synthesis was done via a modified sol-gel method using PVA as polymeric agent. In order to obtain single crystalline phase, it was necessary to use molar ratio Na:Y:P = 1.15:1:2, which is not the stoichiometric, with two calcination steps at 400 ºC / 4 h and 600 ºC / 4 h. Structural characterizations of the synthesized material were performed by X-ray Diffraction and Absorption (XRD and XAS). It was observed that the dopant ions were incorporated into the matrix without changing the structure. Under VUV excitation, the undoped sample presented a luminescent emission spectrum which was attributed to self-trapped exciton recombination. On the other hand, the photoluminescence (PL) of doped samples presented the emission lines characteristic of each dopant. From the photoluminescence excitation curves, 4f-5d transitions were identified for Ce3+, Sm3+ and Tb3+ doped samples and charge transfer processes were noticed for that of Eu3+, Sm3+ and Yb3+. The experimental data of PL was used to determine the positions of the energy levels of all lanthanides (with oxidation states of 3+ or 2+) relative to the valence and conduction bands of NaYP2O7. The model successfully provided the positions of electronic levels within the bandgap, with excellent agreement with the experimental spectra. Thermoluminescence (TL) glow curves were measured for co-doped samples NaYP2O7:Ce3+,Ln3+ (Ln = Dy, Ho and Sm) in order to investigate the nature of the trapping centres. The values determined for the activation energies were comparable with the position of dopant-induced electronic levels, whereas the frequency factor related to the TL peak of Ho-doped sample agreed with the phonon frequency for the lattice. The results indicate that the Ce3+ acts as recombination centre whereas the codopants create electron trap levels.Os objetivos centrais deste trabalho foram a produção e a investigação das propriedades de amostras policristalinas de NaYP2O7 e NaY0.99Ln0.01P2O7 (Ln = Ce, Sm, Eu, Tb e Yb). A produção foi feita por uma rota sol-gel usando PVA como agente polimérico. Para se obter a fase cristalina única, foi necessário utilizar uma razão molar Na:Y:P = 1.15:1:2, que não é a estequiométrica, com duas calcinações, a 400 ºC / 4h e a 600 ºC / 4h. A caracterização estrutural do material produzido foi realizada por Difração e Absorção de raios X (DRX e XAS). Observou-se que os íons dopantes são incorporados à matriz, ocupando o sítio do Y, sem, no entanto, provocar alteração da estrutura cristalina. Sob excitação na região do VUV, amostra não-dopada apresentou um espectro de emissão luminescente que foi atribuído à recombinação de éxcitons auto-armadilhados. Por outro lado, a fotoluminescência (PL) das amostras dopadas apresentou as linhas de emissão características de cada dopante. Nos espectros de excitação da fotoluminescência nestas amostras, as transições 4f-5d foram identificadas para as amostras dopadas com Ce3+, Sm3+ e Tb3+, e processos de transferência de carga para Sm3+, Eu3+ e Yb3+. Os dados experimentais de PL foram usados para determinar as posições dos níveis de energia de todos lantanídeos (com estados de oxidação 3+ ou 2+) em relação à banda de valência e de condução do NaYP2O7. O modelo utilizado forneceu com êxito a posição dos níveis eletrônicos na região proibida, em excelente concordância com os espectros experimentais. Curvas de termoluminescência (TL) foram medidas para amostras co-dopadas NaYP2O7:Ce3+,Ln3+ (Ln = Dy, Ho e Sm) a fim de investigar a natureza dos centros de armadilhamento. Os valores de energia de ativação determinados foram compatíveis com as posições dos níveis eletrônicos determinados por PL e o fator de frequência relacionado ao pico TL da amostra dopada com Ho coincidiu com a frequência de fônons da rede. Os resultados revelaram ainda que o Ce3+ atua como centro de recombinação, enquanto os codopantes são responsáveis pela criação de níveis de armadilhas de elétrons.application/pdfporPropriedades ópticasTerras-rarasLuminescênciaRaios XCompostos de ítrioSódioPropriedades estruturaisDifosfato de sódioDifosfato de nítrioEarths, RareLuminescenceSodiumX-raysCNPQ::CIENCIAS EXATAS E DA TERRA::FISICACaracterização estrutural e óptica do composto NaYP2O7 dopado com terras rarasinfo: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:UFSORIGINALSUELLEN_MARIA_VALERIANO_NOVAIS.pdfapplication/pdf4193199https://ri.ufs.br/jspui/bitstream/riufs/5321/1/SUELLEN_MARIA_VALERIANO_NOVAIS.pdfce5f32a17834824d04efc33e8cfd492eMD51TEXTSUELLEN_MARIA_VALERIANO_NOVAIS.pdf.txtSUELLEN_MARIA_VALERIANO_NOVAIS.pdf.txtExtracted texttext/plain179498https://ri.ufs.br/jspui/bitstream/riufs/5321/2/SUELLEN_MARIA_VALERIANO_NOVAIS.pdf.txta1ab7500c5fc3af460f7b434b712916eMD52THUMBNAILSUELLEN_MARIA_VALERIANO_NOVAIS.pdf.jpgSUELLEN_MARIA_VALERIANO_NOVAIS.pdf.jpgGenerated Thumbnailimage/jpeg1252https://ri.ufs.br/jspui/bitstream/riufs/5321/3/SUELLEN_MARIA_VALERIANO_NOVAIS.pdf.jpg7b042e219dc785e4f9ab77b27ee2fb73MD53riufs/53212019-07-30 19:18:49.59oai:ufs.br:riufs/5321Repositório InstitucionalPUBhttps://ri.ufs.br/oai/requestrepositorio@academico.ufs.bropendoar:2019-07-30T22:18:49Repositório Institucional da UFS - Universidade Federal de Sergipe (UFS)false |
dc.title.por.fl_str_mv |
Caracterização estrutural e óptica do composto NaYP2O7 dopado com terras raras |
title |
Caracterização estrutural e óptica do composto NaYP2O7 dopado com terras raras |
spellingShingle |
Caracterização estrutural e óptica do composto NaYP2O7 dopado com terras raras Novais, Suellen Maria Valeriano Propriedades ópticas Terras-raras Luminescência Raios X Compostos de ítrio Sódio Propriedades estruturais Difosfato de sódio Difosfato de nítrio Earths, Rare Luminescence Sodium X-rays CNPQ::CIENCIAS EXATAS E DA TERRA::FISICA |
title_short |
Caracterização estrutural e óptica do composto NaYP2O7 dopado com terras raras |
title_full |
Caracterização estrutural e óptica do composto NaYP2O7 dopado com terras raras |
title_fullStr |
Caracterização estrutural e óptica do composto NaYP2O7 dopado com terras raras |
title_full_unstemmed |
Caracterização estrutural e óptica do composto NaYP2O7 dopado com terras raras |
title_sort |
Caracterização estrutural e óptica do composto NaYP2O7 dopado com terras raras |
author |
Novais, Suellen Maria Valeriano |
author_facet |
Novais, Suellen Maria Valeriano |
author_role |
author |
dc.contributor.author.fl_str_mv |
Novais, Suellen Maria Valeriano |
dc.contributor.advisor1.fl_str_mv |
Macedo, Zélia Soares |
dc.contributor.authorLattes.fl_str_mv |
http://lattes.cnpq.br/4216632365210465 |
contributor_str_mv |
Macedo, Zélia Soares |
dc.subject.por.fl_str_mv |
Propriedades ópticas Terras-raras Luminescência Raios X Compostos de ítrio Sódio Propriedades estruturais Difosfato de sódio Difosfato de nítrio |
topic |
Propriedades ópticas Terras-raras Luminescência Raios X Compostos de ítrio Sódio Propriedades estruturais Difosfato de sódio Difosfato de nítrio Earths, Rare Luminescence Sodium X-rays CNPQ::CIENCIAS EXATAS E DA TERRA::FISICA |
dc.subject.eng.fl_str_mv |
Earths, Rare Luminescence Sodium X-rays |
dc.subject.cnpq.fl_str_mv |
CNPQ::CIENCIAS EXATAS E DA TERRA::FISICA |
description |
The aims of this work were to produce and investigate the properties of NaYP2O7 and NaY0.99Ln0.01P2O7 (Ln = Ce, Sm, Eu, Tb and Yb) polycrystalline samples. The synthesis was done via a modified sol-gel method using PVA as polymeric agent. In order to obtain single crystalline phase, it was necessary to use molar ratio Na:Y:P = 1.15:1:2, which is not the stoichiometric, with two calcination steps at 400 ºC / 4 h and 600 ºC / 4 h. Structural characterizations of the synthesized material were performed by X-ray Diffraction and Absorption (XRD and XAS). It was observed that the dopant ions were incorporated into the matrix without changing the structure. Under VUV excitation, the undoped sample presented a luminescent emission spectrum which was attributed to self-trapped exciton recombination. On the other hand, the photoluminescence (PL) of doped samples presented the emission lines characteristic of each dopant. From the photoluminescence excitation curves, 4f-5d transitions were identified for Ce3+, Sm3+ and Tb3+ doped samples and charge transfer processes were noticed for that of Eu3+, Sm3+ and Yb3+. The experimental data of PL was used to determine the positions of the energy levels of all lanthanides (with oxidation states of 3+ or 2+) relative to the valence and conduction bands of NaYP2O7. The model successfully provided the positions of electronic levels within the bandgap, with excellent agreement with the experimental spectra. Thermoluminescence (TL) glow curves were measured for co-doped samples NaYP2O7:Ce3+,Ln3+ (Ln = Dy, Ho and Sm) in order to investigate the nature of the trapping centres. The values determined for the activation energies were comparable with the position of dopant-induced electronic levels, whereas the frequency factor related to the TL peak of Ho-doped sample agreed with the phonon frequency for the lattice. The results indicate that the Ce3+ acts as recombination centre whereas the codopants create electron trap levels. |
publishDate |
2014 |
dc.date.issued.fl_str_mv |
2014-02-18 |
dc.date.accessioned.fl_str_mv |
2017-09-26T18:27:24Z |
dc.date.available.fl_str_mv |
2017-09-26T18:27:24Z |
dc.type.status.fl_str_mv |
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dc.type.driver.fl_str_mv |
info:eu-repo/semantics/doctoralThesis |
format |
doctoralThesis |
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publishedVersion |
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https://ri.ufs.br/handle/riufs/5321 |
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dc.language.iso.fl_str_mv |
por |
language |
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info:eu-repo/semantics/openAccess |
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openAccess |
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Pós-Graduação em Física |
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