Estudo de pós cerâmicos de PbTiO3 utilizando-se o método dos precursores poliméricos.
Autor(a) principal: | |
---|---|
Data de Publicação: | 2000 |
Tipo de documento: | Dissertação |
Idioma: | por |
Título da fonte: | Repositório Institucional da UFSCAR |
Texto Completo: | https://repositorio.ufscar.br/handle/ufscar/6508 |
Resumo: | THE STUDY OF PbTiO3 (PT) CERAMIC POWDERS USING THE POLYMERIC PRECURSOR METHOD was started by the preparation of a precursor solution of metallic cations. Citric acid was used as quelation agent and ethylene glycol as esterification and polymerization agent. This solution was submitted to thermal treatment at temperatures about 300°C for the pyrolysis of the obtained polyester. PT crystalline powders were obtained starting from amorphous precursors, varying the calcination conditions as the temperature, the time and the furnace atmosphere. The evolution of the crystallization process of the PT was accompanied by X-ray diffraction (XRD), Raman spectroscopy and infrared spectroscopy (FTIR). It was verified that the beginning of the crystallization of the PT occurs at a temperature below the Curie temperature of the material (~ 490°C). Heat treatments for one hour at 400°C yields PT crystalline and free of secondary phases. It was observed that the formation of the PT phase takes place without the formation of an intermediary carbonate phase that can occur in perovskites obtained by the polymeric precursor method. It was verified that there was no formation of pyrochlore or fluorite intermediary crystalline phase, and the only intermediary phase found was cubic PT in some calcination stages. This indicates that the polymeric precursor method provides the homogenization of the ions at the molecular level, during the synthesis process. Aiming at a better understanding of the crystallization process, a comparison was performed between the amorphous and crystalline powders by means of X-ray absorption, using EXAFS (Extended X-Ray Absorption Fine Structure) and XANES (X-Ray Absorption Near Edge Structure) spectra. It was thus verified that the amorphous powders present a short distance structure formed by sixfold oxygen titanium coordination coexisting with fivefold oxygen titanium coordination. Photoluminescent property at room temperature was detected in the amorphous powders. It was verified by reflectance spectra the presence of a tail and of optical exponential borders which are characteristic of amorphous semiconductors. It was also verified that these tail and borders are sensitive to the temperature and to the time of calcination. With the increase of the degree of crystallization of the material and the consequent ordering of the crystalline phase, this luminescent property disappears. By means of theoretical calculations it was possible to verify that the amorphous powder induces electronic levels in the area of the band gap of the material. This fact favors the recombination of the electron-hole pair, which is possibly the responsible for the photoluminescence. |
id |
SCAR_54550f343c164679b46b860da97a8de1 |
---|---|
oai_identifier_str |
oai:repositorio.ufscar.br:ufscar/6508 |
network_acronym_str |
SCAR |
network_name_str |
Repositório Institucional da UFSCAR |
repository_id_str |
4322 |
spelling |
Paris, Elaine CristinaSilva, Elson Longo dahttp://lattes.cnpq.br/9848311210578810http://genos.cnpq.br:12010/dwlattes/owa/prc_imp_cv_int?f_cod=K4700940J82b06dcbe-d595-48de-ad9e-26077464fa042016-06-02T20:36:34Z2005-01-112016-06-02T20:36:34Z2000-11-30PARIS, Elaine Cristina. Study of PbTiO3 (PT) ceramic powers using the polymeric precursor method.. 2000. 106 f. Dissertação (Mestrado em Ciências Exatas e da Terra) - Universidade Federal de São Carlos, São Carlos, 2000.https://repositorio.ufscar.br/handle/ufscar/6508THE STUDY OF PbTiO3 (PT) CERAMIC POWDERS USING THE POLYMERIC PRECURSOR METHOD was started by the preparation of a precursor solution of metallic cations. Citric acid was used as quelation agent and ethylene glycol as esterification and polymerization agent. This solution was submitted to thermal treatment at temperatures about 300°C for the pyrolysis of the obtained polyester. PT crystalline powders were obtained starting from amorphous precursors, varying the calcination conditions as the temperature, the time and the furnace atmosphere. The evolution of the crystallization process of the PT was accompanied by X-ray diffraction (XRD), Raman spectroscopy and infrared spectroscopy (FTIR). It was verified that the beginning of the crystallization of the PT occurs at a temperature below the Curie temperature of the material (~ 490°C). Heat treatments for one hour at 400°C yields PT crystalline and free of secondary phases. It was observed that the formation of the PT phase takes place without the formation of an intermediary carbonate phase that can occur in perovskites obtained by the polymeric precursor method. It was verified that there was no formation of pyrochlore or fluorite intermediary crystalline phase, and the only intermediary phase found was cubic PT in some calcination stages. This indicates that the polymeric precursor method provides the homogenization of the ions at the molecular level, during the synthesis process. Aiming at a better understanding of the crystallization process, a comparison was performed between the amorphous and crystalline powders by means of X-ray absorption, using EXAFS (Extended X-Ray Absorption Fine Structure) and XANES (X-Ray Absorption Near Edge Structure) spectra. It was thus verified that the amorphous powders present a short distance structure formed by sixfold oxygen titanium coordination coexisting with fivefold oxygen titanium coordination. Photoluminescent property at room temperature was detected in the amorphous powders. It was verified by reflectance spectra the presence of a tail and of optical exponential borders which are characteristic of amorphous semiconductors. It was also verified that these tail and borders are sensitive to the temperature and to the time of calcination. With the increase of the degree of crystallization of the material and the consequent ordering of the crystalline phase, this luminescent property disappears. By means of theoretical calculations it was possible to verify that the amorphous powder induces electronic levels in the area of the band gap of the material. This fact favors the recombination of the electron-hole pair, which is possibly the responsible for the photoluminescence.NO ESTUDO DE PÓS CERÂMICOS DE PbTiO3 (PT) UTILIZANDO-SE O MÉTODO DOS PRECURSORES POLIMÉRICOS, foi preparada uma solução precursora de cátions métálicos, empregando-se ácido cítrico como agente quelante e etilenoglicol como agente esterificante e polimerizante. Esta solução, foi submetida ao tratamento térmico, à temperaturas ao redor de 300 C, para a pirólise do poliéster obtido. Os pós de PT cristalinos, foram obtidos a partir de precursores amorfos, variando-se as condições de calcinação como a temperatura, o tempo e a utilização ou não de fluxo de gases. A evolução do processo de cristalização do PT foi acompanhada por difração de raios X (DRX), espectroscopia Raman e espectrofotometria na região do infravermelho (FTIR). Verificou-se que o início da cristalização do PT ocorre a uma temperatura inferior à temperatura de Curie do material (~ 490 C). A partir de 400 C por uma hora de calcinação foi obtido PT cristalino e livre de fases secundárias. Observou-se que a formação da fase PT ocorre sem formação de fase intermediária de carbonato, que pode ser obtida na obtenção de perovisquitas pelo método dos precursores poliméricos. Verificou-se que não houve a formação de fase cristalina intermediária como pirocloro ou fluorita, sendo que só a fase PT cúbica foi encontrada como fase intermedária em alguns estágios de calcinação. Isto indica, que o método dos precursores poliméricos proporciona a homogenidade dos íons em nível molecular, durante o processo de síntese. Para uma compreensão de como ocorre o processo de cristalização, foi realizada uma comparação entre pós amorfos e cristalinos por absorção de raios X, por intermédio de espectros EXAFS (Extended X-Ray Absorption Fine Structure) e XANES (X-Ray Absorption Near Edge Structure). Com isto, verificou-se que os pós amorfos apresentam uma estrutura à curta distância formada por titânio hexacoordenado por oxigênio coexistindo com titânio pentacoordenado. Foi detectada propriedade fotoluminescente para os pós amorfos à temperatura ambiente, em que se verificou por espectros de reflectância a presença de uma cauda e de bordas ópticas exponenciais características de semicondutores amorfos. Verificou-se que estas caudas e bordas são sensíveis à temperatura e ao tempo de calcinação. Com o aumento da cristalização do material, com a conseqüente ordenação da fase cristalina, esta propriedade luminescente desaparece. Utilizando-se cálculos teóricos foi possível verificar que o pó amorfo, induz a formação de níveis eletrônicos na região da banda gap do material. Fato, que favorece a recombinação do par elétron-buraco, que possivelmente é o responsável pela fotoluminescência.Universidade Federal de Minas Geraisapplication/pdfporUniversidade Federal de São CarlosPrograma de Pós-Graduação em Química - PPGQUFSCarBRFísico-químicaTitanato de chumboMétodo dos precursores poliméricospó de cerâmica - sínteseLuminescênciaCIENCIAS EXATAS E DA TERRA::QUIMICA::FISICO-QUIMICAEstudo de pós cerâmicos de PbTiO3 utilizando-se o método dos precursores poliméricos.Study of PbTiO3 (PT) ceramic powers using the polymeric precursor method.info:eu-repo/semantics/publishedVersioninfo:eu-repo/semantics/masterThesis-1-1858e0964-d787-4b05-8cfd-92ebfc20599einfo:eu-repo/semantics/openAccessreponame:Repositório Institucional da UFSCARinstname:Universidade Federal de São Carlos (UFSCAR)instacron:UFSCARORIGINALDissECP.pdfapplication/pdf9517321https://repositorio.ufscar.br/bitstream/ufscar/6508/1/DissECP.pdfe528d9311d42f94d3167e859e7d873b1MD51THUMBNAILDissECP.pdf.jpgDissECP.pdf.jpgIM Thumbnailimage/jpeg10419https://repositorio.ufscar.br/bitstream/ufscar/6508/2/DissECP.pdf.jpg13190a1d71b5cb37b8e1b9e88cdfe912MD52ufscar/65082023-09-18 18:31:11.839oai:repositorio.ufscar.br:ufscar/6508Repositório InstitucionalPUBhttps://repositorio.ufscar.br/oai/requestopendoar:43222023-09-18T18:31:11Repositório Institucional da UFSCAR - Universidade Federal de São Carlos (UFSCAR)false |
dc.title.por.fl_str_mv |
Estudo de pós cerâmicos de PbTiO3 utilizando-se o método dos precursores poliméricos. |
dc.title.alternative.eng.fl_str_mv |
Study of PbTiO3 (PT) ceramic powers using the polymeric precursor method. |
title |
Estudo de pós cerâmicos de PbTiO3 utilizando-se o método dos precursores poliméricos. |
spellingShingle |
Estudo de pós cerâmicos de PbTiO3 utilizando-se o método dos precursores poliméricos. Paris, Elaine Cristina Físico-química Titanato de chumbo Método dos precursores poliméricos pó de cerâmica - síntese Luminescência CIENCIAS EXATAS E DA TERRA::QUIMICA::FISICO-QUIMICA |
title_short |
Estudo de pós cerâmicos de PbTiO3 utilizando-se o método dos precursores poliméricos. |
title_full |
Estudo de pós cerâmicos de PbTiO3 utilizando-se o método dos precursores poliméricos. |
title_fullStr |
Estudo de pós cerâmicos de PbTiO3 utilizando-se o método dos precursores poliméricos. |
title_full_unstemmed |
Estudo de pós cerâmicos de PbTiO3 utilizando-se o método dos precursores poliméricos. |
title_sort |
Estudo de pós cerâmicos de PbTiO3 utilizando-se o método dos precursores poliméricos. |
author |
Paris, Elaine Cristina |
author_facet |
Paris, Elaine Cristina |
author_role |
author |
dc.contributor.authorlattes.por.fl_str_mv |
http://genos.cnpq.br:12010/dwlattes/owa/prc_imp_cv_int?f_cod=K4700940J8 |
dc.contributor.author.fl_str_mv |
Paris, Elaine Cristina |
dc.contributor.advisor1.fl_str_mv |
Silva, Elson Longo da |
dc.contributor.advisor1Lattes.fl_str_mv |
http://lattes.cnpq.br/9848311210578810 |
dc.contributor.authorID.fl_str_mv |
2b06dcbe-d595-48de-ad9e-26077464fa04 |
contributor_str_mv |
Silva, Elson Longo da |
dc.subject.por.fl_str_mv |
Físico-química Titanato de chumbo Método dos precursores poliméricos pó de cerâmica - síntese Luminescência |
topic |
Físico-química Titanato de chumbo Método dos precursores poliméricos pó de cerâmica - síntese Luminescência CIENCIAS EXATAS E DA TERRA::QUIMICA::FISICO-QUIMICA |
dc.subject.cnpq.fl_str_mv |
CIENCIAS EXATAS E DA TERRA::QUIMICA::FISICO-QUIMICA |
description |
THE STUDY OF PbTiO3 (PT) CERAMIC POWDERS USING THE POLYMERIC PRECURSOR METHOD was started by the preparation of a precursor solution of metallic cations. Citric acid was used as quelation agent and ethylene glycol as esterification and polymerization agent. This solution was submitted to thermal treatment at temperatures about 300°C for the pyrolysis of the obtained polyester. PT crystalline powders were obtained starting from amorphous precursors, varying the calcination conditions as the temperature, the time and the furnace atmosphere. The evolution of the crystallization process of the PT was accompanied by X-ray diffraction (XRD), Raman spectroscopy and infrared spectroscopy (FTIR). It was verified that the beginning of the crystallization of the PT occurs at a temperature below the Curie temperature of the material (~ 490°C). Heat treatments for one hour at 400°C yields PT crystalline and free of secondary phases. It was observed that the formation of the PT phase takes place without the formation of an intermediary carbonate phase that can occur in perovskites obtained by the polymeric precursor method. It was verified that there was no formation of pyrochlore or fluorite intermediary crystalline phase, and the only intermediary phase found was cubic PT in some calcination stages. This indicates that the polymeric precursor method provides the homogenization of the ions at the molecular level, during the synthesis process. Aiming at a better understanding of the crystallization process, a comparison was performed between the amorphous and crystalline powders by means of X-ray absorption, using EXAFS (Extended X-Ray Absorption Fine Structure) and XANES (X-Ray Absorption Near Edge Structure) spectra. It was thus verified that the amorphous powders present a short distance structure formed by sixfold oxygen titanium coordination coexisting with fivefold oxygen titanium coordination. Photoluminescent property at room temperature was detected in the amorphous powders. It was verified by reflectance spectra the presence of a tail and of optical exponential borders which are characteristic of amorphous semiconductors. It was also verified that these tail and borders are sensitive to the temperature and to the time of calcination. With the increase of the degree of crystallization of the material and the consequent ordering of the crystalline phase, this luminescent property disappears. By means of theoretical calculations it was possible to verify that the amorphous powder induces electronic levels in the area of the band gap of the material. This fact favors the recombination of the electron-hole pair, which is possibly the responsible for the photoluminescence. |
publishDate |
2000 |
dc.date.issued.fl_str_mv |
2000-11-30 |
dc.date.available.fl_str_mv |
2005-01-11 2016-06-02T20:36:34Z |
dc.date.accessioned.fl_str_mv |
2016-06-02T20:36:34Z |
dc.type.status.fl_str_mv |
info:eu-repo/semantics/publishedVersion |
dc.type.driver.fl_str_mv |
info:eu-repo/semantics/masterThesis |
format |
masterThesis |
status_str |
publishedVersion |
dc.identifier.citation.fl_str_mv |
PARIS, Elaine Cristina. Study of PbTiO3 (PT) ceramic powers using the polymeric precursor method.. 2000. 106 f. Dissertação (Mestrado em Ciências Exatas e da Terra) - Universidade Federal de São Carlos, São Carlos, 2000. |
dc.identifier.uri.fl_str_mv |
https://repositorio.ufscar.br/handle/ufscar/6508 |
identifier_str_mv |
PARIS, Elaine Cristina. Study of PbTiO3 (PT) ceramic powers using the polymeric precursor method.. 2000. 106 f. Dissertação (Mestrado em Ciências Exatas e da Terra) - Universidade Federal de São Carlos, São Carlos, 2000. |
url |
https://repositorio.ufscar.br/handle/ufscar/6508 |
dc.language.iso.fl_str_mv |
por |
language |
por |
dc.relation.confidence.fl_str_mv |
-1 -1 |
dc.relation.authority.fl_str_mv |
858e0964-d787-4b05-8cfd-92ebfc20599e |
dc.rights.driver.fl_str_mv |
info:eu-repo/semantics/openAccess |
eu_rights_str_mv |
openAccess |
dc.format.none.fl_str_mv |
application/pdf |
dc.publisher.none.fl_str_mv |
Universidade Federal de São Carlos |
dc.publisher.program.fl_str_mv |
Programa de Pós-Graduação em Química - PPGQ |
dc.publisher.initials.fl_str_mv |
UFSCar |
dc.publisher.country.fl_str_mv |
BR |
publisher.none.fl_str_mv |
Universidade Federal de São Carlos |
dc.source.none.fl_str_mv |
reponame:Repositório Institucional da UFSCAR instname:Universidade Federal de São Carlos (UFSCAR) instacron:UFSCAR |
instname_str |
Universidade Federal de São Carlos (UFSCAR) |
instacron_str |
UFSCAR |
institution |
UFSCAR |
reponame_str |
Repositório Institucional da UFSCAR |
collection |
Repositório Institucional da UFSCAR |
bitstream.url.fl_str_mv |
https://repositorio.ufscar.br/bitstream/ufscar/6508/1/DissECP.pdf https://repositorio.ufscar.br/bitstream/ufscar/6508/2/DissECP.pdf.jpg |
bitstream.checksum.fl_str_mv |
e528d9311d42f94d3167e859e7d873b1 13190a1d71b5cb37b8e1b9e88cdfe912 |
bitstream.checksumAlgorithm.fl_str_mv |
MD5 MD5 |
repository.name.fl_str_mv |
Repositório Institucional da UFSCAR - Universidade Federal de São Carlos (UFSCAR) |
repository.mail.fl_str_mv |
|
_version_ |
1802136295352303616 |