Estudo do comportamento PTCR em cerâmicas de BCT dopadas com íons terra raras

Detalhes bibliográficos
Ano de defesa: 2012
Autor(a) principal: Santos, Jerre Cristiano Alves dos lattes
Orientador(a): Silva, Ronaldo Santos da lattes
Banca de defesa: Não Informado pela instituição
Tipo de documento: Dissertação
Tipo de acesso: Acesso aberto
Idioma: por
Instituição de defesa: Universidade Federal de Sergipe
Programa de Pós-Graduação: Pós-Graduação em Física
Departamento: Não Informado pela instituição
País: BR
Palavras-chave em Português:
Palavras-chave em Inglês:
Área do conhecimento CNPq:
Link de acesso: https://ri.ufs.br/handle/riufs/5346
Resumo: Barium titanate (BaTiO3 - BT) is a ferroelectric material with important technological applications. When partially doped with trivalent cations at the barium sublattice or pentavalent at the titanium sublattice, BaTiO3-based ceramics exhibit a semiconductive character, accompanied by a Positive Temperature Coefficient of Resistivity (PTCR). Several ways of BT modifications have been proposed in literature, as example, the use of different synthesis methods and the doping with different ions. Therefore, in the present work we have as objective the synthesis, sintering and electrical characterization of the rare earth ions (RE = La3+, Y3+, Er3+, Nd3+ e Eu3+) doped barium calcium titanate ceramics (Ba0,77Ca0,227RE0,003TiO3 BCT_RE) in order to study mainly the PTCR behavior. The powder synthesis was done by the polymeric precursor method followed by the sinterization at reducing atmosphere during the heating up ramp and different atmosphere during cooling down ramp in order to investigate the atmosphere and dopant effect on PTCR behavior. The characterization was done using the Differential Thermal Analysis, Thermogravimetry, Scanning Differential Calorimetry, X-ray Powder Diffraction, Scanning Electron Microscopy and Impedance Spectroscopy techniques. The calcined powder at 600ºC/4h presented majority BCT phase and after sintering at 1350ºC/6h, a small amount of Ba6Ti17O40 phase was observed. The sintered ceramics presented a homogeneous grain size distribution but with the presence of a secondary phase at the grain boundary for all compositions, and Curie temperature at about 120ºC. The PTCR characteristics of the ceramics were studied as a function of the sintering atmosphere and dopant type. In summary, all the samples, exception of the Eu doped samples, presented PTCR behavior in all the studied conditions. .