Microstructure effects on the thermoelectric response of doped SrTiO3

Detalhes bibliográficos
Autor(a) principal: Resende, João Avelãs
Data de Publicação: 2013
Tipo de documento: Dissertação
Idioma: eng
Título da fonte: Repositório Científico de Acesso Aberto de Portugal (Repositórios Cientìficos)
Texto Completo: http://hdl.handle.net/10773/12581
Resumo: Niobium doped SrTiO3 ceramics were prepared with varying density and grain size in order to study the effect on the thermoelectric properties and discover a possible way to enhance the figure of merit (ZT = S2 .σ.T.κ-1) of this oxide. The samples were prepared by the conventional solid-state reaction technique and the grain-size variation was carried-out by the variation of precursor powders, sintering and annealing time. Structural and microstructural characterization were carried-out by XRD, electron microscopy (SEM) and optical microscope (OM). The relative density was measured by Archimedes principle, with the theoretical densities calculated from the XRD spectra. The electrical resistivity and Seebeck coefficient were measured by ZEM-3. The thermal diffusivity was measured using a Laser Flash technique and the specific heat was measure by Differential Scanning Calorimetry (DSC), in order to obtain the thermal conductivity indirectly. The different doping compositions (5% and 20%) conjugated with the variations in density and grain size in the samples shows a potential way to improve ZT. While in the less doped samples, the higher ZT is related to the annealing time combined with larger grains and density; in the 20% Nb doped samples the smaller grain size and higher density, enhance the ZT values. The highest figure of merit obtained is 0.44 for 20% Nb doped composition, with a bimodal grain distribution. The value is the highest obtained for a Niobium doped SrTiO3 ceramic.
id RCAP_9d665694fb5e7a79fab6e38e6cf04263
oai_identifier_str oai:ria.ua.pt:10773/12581
network_acronym_str RCAP
network_name_str Repositório Científico de Acesso Aberto de Portugal (Repositórios Cientìficos)
repository_id_str 7160
spelling Microstructure effects on the thermoelectric response of doped SrTiO3Engenharia de materiaisTermoelectricidadeTitanato de estrôncioCerâmica ferroeléctricaNiobium doped SrTiO3 ceramics were prepared with varying density and grain size in order to study the effect on the thermoelectric properties and discover a possible way to enhance the figure of merit (ZT = S2 .σ.T.κ-1) of this oxide. The samples were prepared by the conventional solid-state reaction technique and the grain-size variation was carried-out by the variation of precursor powders, sintering and annealing time. Structural and microstructural characterization were carried-out by XRD, electron microscopy (SEM) and optical microscope (OM). The relative density was measured by Archimedes principle, with the theoretical densities calculated from the XRD spectra. The electrical resistivity and Seebeck coefficient were measured by ZEM-3. The thermal diffusivity was measured using a Laser Flash technique and the specific heat was measure by Differential Scanning Calorimetry (DSC), in order to obtain the thermal conductivity indirectly. The different doping compositions (5% and 20%) conjugated with the variations in density and grain size in the samples shows a potential way to improve ZT. While in the less doped samples, the higher ZT is related to the annealing time combined with larger grains and density; in the 20% Nb doped samples the smaller grain size and higher density, enhance the ZT values. The highest figure of merit obtained is 0.44 for 20% Nb doped composition, with a bimodal grain distribution. The value is the highest obtained for a Niobium doped SrTiO3 ceramic.Amostras cerâmicas de SrTiO3 dopadas com Nióbio foram preparadas com diferentes densidades e tamanhos de grão, de forma a estudar o efeito sobre as propriedades termoelétricas e descobrir uma maneira possível para aumentar a sua figura de mérito (ZT = S2 .σ.T.κ-1). As amostras foram preparadas por reação em estado sólido convencional e a variação de dimensão de grão foi efectuada pelos variação dos pós precursores, tempo de sinterização e tempo de recozimento. A caracterização estrutural e microestrutural foram realizadas por DRX, microscopia eletrônica de varredura (MEV) e microscopia óptica (OM). A densidade foi medida pelo princípio de Arquimedes, com as densidades teóricos calculados a partir dos espectros de DRX. A resistência eléctrica e o coeficiente de Seebeck foram medidos por ZEM-3. A difusividade térmica foi medida utilizando a técnica de Flash-laser e o calor específico foi medido por Calorimetria Diferencial (DSC), com o objectivo de obter a condutividade térmica indiretamente. As diferentes composições de dopagem (5% e 20%) conjugados com as variações na densidade e tamanho de grão nas amostras mostram uma via potencial para melhorar ZT. Enquanto que nas amostras menos dopadas, a maior ZT está relacionado com o tempo de recozimento combinado com grãos de maior dimensão e densidade; nas amostras dopadas com 20% de nióbio o menor tamanho de grão menor e maior densidade aumentam os valores da figura de mérito. O valor mais elevado da figura de mérito obtido é de 0,44 para a composição dopada com 20% de Nb e com uma distribuição bimodal de grãos. O valor é o mais elevado para um cerâmico de SrTiO3 dopado com Nb.Universidade de Aveiro2018-07-20T14:00:46Z2013-12-19T00:00:00Z2013-12-192016-01-07T11:00:00Zinfo:eu-repo/semantics/publishedVersioninfo:eu-repo/semantics/masterThesisapplication/pdfhttp://hdl.handle.net/10773/12581TID:201579421engResende, João Avelãsinfo:eu-repo/semantics/openAccessreponame:Repositório Científico de Acesso Aberto de Portugal (Repositórios Cientìficos)instname:Agência para a Sociedade do Conhecimento (UMIC) - FCT - Sociedade da Informaçãoinstacron:RCAAP2024-02-22T11:22:59Zoai:ria.ua.pt:10773/12581Portal AgregadorONGhttps://www.rcaap.pt/oai/openaireopendoar:71602024-03-20T02:48:44.601043Repositório Científico de Acesso Aberto de Portugal (Repositórios Cientìficos) - Agência para a Sociedade do Conhecimento (UMIC) - FCT - Sociedade da Informaçãofalse
dc.title.none.fl_str_mv Microstructure effects on the thermoelectric response of doped SrTiO3
title Microstructure effects on the thermoelectric response of doped SrTiO3
spellingShingle Microstructure effects on the thermoelectric response of doped SrTiO3
Resende, João Avelãs
Engenharia de materiais
Termoelectricidade
Titanato de estrôncio
Cerâmica ferroeléctrica
title_short Microstructure effects on the thermoelectric response of doped SrTiO3
title_full Microstructure effects on the thermoelectric response of doped SrTiO3
title_fullStr Microstructure effects on the thermoelectric response of doped SrTiO3
title_full_unstemmed Microstructure effects on the thermoelectric response of doped SrTiO3
title_sort Microstructure effects on the thermoelectric response of doped SrTiO3
author Resende, João Avelãs
author_facet Resende, João Avelãs
author_role author
dc.contributor.author.fl_str_mv Resende, João Avelãs
dc.subject.por.fl_str_mv Engenharia de materiais
Termoelectricidade
Titanato de estrôncio
Cerâmica ferroeléctrica
topic Engenharia de materiais
Termoelectricidade
Titanato de estrôncio
Cerâmica ferroeléctrica
description Niobium doped SrTiO3 ceramics were prepared with varying density and grain size in order to study the effect on the thermoelectric properties and discover a possible way to enhance the figure of merit (ZT = S2 .σ.T.κ-1) of this oxide. The samples were prepared by the conventional solid-state reaction technique and the grain-size variation was carried-out by the variation of precursor powders, sintering and annealing time. Structural and microstructural characterization were carried-out by XRD, electron microscopy (SEM) and optical microscope (OM). The relative density was measured by Archimedes principle, with the theoretical densities calculated from the XRD spectra. The electrical resistivity and Seebeck coefficient were measured by ZEM-3. The thermal diffusivity was measured using a Laser Flash technique and the specific heat was measure by Differential Scanning Calorimetry (DSC), in order to obtain the thermal conductivity indirectly. The different doping compositions (5% and 20%) conjugated with the variations in density and grain size in the samples shows a potential way to improve ZT. While in the less doped samples, the higher ZT is related to the annealing time combined with larger grains and density; in the 20% Nb doped samples the smaller grain size and higher density, enhance the ZT values. The highest figure of merit obtained is 0.44 for 20% Nb doped composition, with a bimodal grain distribution. The value is the highest obtained for a Niobium doped SrTiO3 ceramic.
publishDate 2013
dc.date.none.fl_str_mv 2013-12-19T00:00:00Z
2013-12-19
2016-01-07T11:00:00Z
2018-07-20T14:00:46Z
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.uri.fl_str_mv http://hdl.handle.net/10773/12581
TID:201579421
url http://hdl.handle.net/10773/12581
identifier_str_mv TID:201579421
dc.language.iso.fl_str_mv eng
language eng
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 de Aveiro
publisher.none.fl_str_mv Universidade de Aveiro
dc.source.none.fl_str_mv reponame:Repositório Científico de Acesso Aberto de Portugal (Repositórios Cientìficos)
instname:Agência para a Sociedade do Conhecimento (UMIC) - FCT - Sociedade da Informação
instacron:RCAAP
instname_str Agência para a Sociedade do Conhecimento (UMIC) - FCT - Sociedade da Informação
instacron_str RCAAP
institution RCAAP
reponame_str Repositório Científico de Acesso Aberto de Portugal (Repositórios Cientìficos)
collection Repositório Científico de Acesso Aberto de Portugal (Repositórios Cientìficos)
repository.name.fl_str_mv Repositório Científico de Acesso Aberto de Portugal (Repositórios Cientìficos) - Agência para a Sociedade do Conhecimento (UMIC) - FCT - Sociedade da Informação
repository.mail.fl_str_mv
_version_ 1799137538122711040