Caracterização elétrica e dielétrica de cerâmicas de BaTiO3 e Ba0,77Ca0,23TiO3 sintetizadas pelo método sol gel proteico

• Ano de defesa: 2012
• Autor(a) principal: Sampaio, David Vieira
• Orientador(a): Silva, Ronaldo Santos da
• 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
• País: BR
• Palavras-chave em Português: Caracterização elétrica; Caracterização dielétrica; Método sol gel proteico
• Palavras-chave em Inglês: Electrical characterization; Dielectric characterization; Sol protein gel
• Área do conhecimento CNPq: CNPQ::CIENCIAS EXATAS E DA TERRA::FISICA
• Link de acesso: https://ri.ufs.br/handle/riufs/5349

Barium Titanate (BaTiO3 BT) based Ceramic materials have a wide industrial application as Multilayer Ceramic Capacitors (MLCCs) mainly due to its high dielectric constant and good capacitance stability with the temperature change, however this material also presents some limitations, for example, oxidation of low cost electrodes. 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, the present work had as objectives the synthesis, sintering and electrical characterization of the BaTiO3 and Ba0.77Ca0.23TiO3 (Barium Calcium Titanate) ceramics. The Sol Gel Proteic method was used to powder synthesis, in this method, coconut water is employed as polymeric agent instead of the conventional alcoxide precursors. The characterization was done using the differential thermal analysis, thermogravimetry, x-ray powder diffraction, scanning electron microscopy and impedance spectroscopy techniques. Both, the calcined powders at 1100 °C and the sintered ceramics at 1350 °C presented single crystalline phase, with good microstructural homogeneity and relative density higher than 90%. The sintered ceramics presented a dielectric constant value at room temperature of 1200 (BT) and 680 (BCT), and dielectric loss of 4,8% (BT) and 1,8% (BCT). Besides, the BCT ceramics presented a Curie temperature on average 14 °C above that observed in Literature. Finally, the activation energies of the conductive process of the grain an grain boundary regions were evaluated following two distinct methods using: i) the Brick-layer model; and ii) the average relaxation frequency of each ceramic region, grain and grain boundary. The obtained values by the two methods are in accordance with them and suggest that the dominant conduction mechanism occurs by oxygen vacancy diffusion created still during the sintering process.