Investigação das propriedades físicas do sistema titanato de bário modificado com íons doadores nos sítios A e/ou B
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Data
2017-08-18
Autores
Oliveira, Marco Aurélio de [UNESP]
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Universidade Estadual Paulista (Unesp)
Resumo
O titanato de bário (BaTiO3, BT) é um material ferroelétrico com diversas aplicações, dentro do mercado de componentes eletrônicos, devido às excelentes propriedades físicas que manifesta, em relação a outros sistemas ferroelétricos, continuando a atrair durante várias décadas o interesse científico e comercial. Dentre o grande número de trabalhos sobre o sistema BT reportados na literatura muitos são associados à vasta gama de aplicações para a indústria eletro-eletrônica, dentre as quais se destacam o uso em dispositivos para capacitores, termistores, entre outros. A dopagem do BaTiO3 com íons doadores implica na mudança de algumas propriedades físicas, que conduzem a comportamentos anómalos em determinados parâmetros físicos, cuja natureza ainda não tem sido muito esclarecida, embora muitos trabalhos tenham se empenhado para tentar justificar tais efeitos. Neste contexto, neste trabalho, as propriedades físicas do sistema BaTiO3 serão investigadas considerando a adição de elementos doadores, nos sítios A e B da estrutura. Em particular, os íons de gadolínio (Gd3+) e nióbio (Nb5+) serão usados como modificadores da estrutura perovskita em substituição dos íons de bário (Ba2+) e titânio (Ti4+) nos sítios A e B, respectivamente, considerando as fórmulas químicas Ba1-xGdxTiO3 e BaTi1-x NbxO3 (sendo x = 0.001, 0.002, 0.003, 0.004 e 0.005). As propriedades estruturais e microestruturais foram investigadas à temperatura ambiente, enquanto as propriedades dielétricas e elétricas foram analisadas em uma ampla faixa de temperatura e frequência. Em particular, os efeitos condutivos proporcionados pela dopagem dos íons doadores em diferentes sítios cristalográficos, cujo estudo ainda não foi reportado na literatura, foram cuidadosamente investigados para melhor compreender os fatores que influenciam e determinam as propriedades semicondutoras de tais materiais, visando aprimorar no entendimento a nível microscópico e macroscópico dos fatores que influenciam e originam os mecanismos condutivos nestes materiais, fatores determinantes para uma posterior aplicação na indústria eletroeletrônica. Os materiais foram obtidos a partir do método de Pechini (ou Método dos Precursores Poliméricos), bem conhecido na literatura por ser um método muito eficiente, quando comparado com métodos convencionais para síntese de materiais policristalinos, pois apresenta inúmeras vantagens, tais como a síntese em baixas temperaturas, baixa contaminação, maior controle estequiométrico, alta homogeneização e possibilidade de obtenção de pós em escala nanométrica.
Barium titanate (BaTiO3, BT) is a ferroelectric material with several applications for the electronic components market, due to its excellent physical properties when compared to other ferroelectric systems. So that, BT continues up today attracting the scientific and commercial interest for several decades. Among the large number of papers on the BT system reported in the literature, many are associated with the wide range of applications in the electric and electronic industry, where the use in capacitors, thermistors and other devices stands out. By doping BaTiO3 with donor ions implies in the change of some physical properties leading to abnormal behaviors in certain physical parameters. The nature of these changes is not yet very clear, although many papers have been reported trying to justify such effects. In this context, this work aims the investigation of the physical properties of the BaTiO3 system, considering the addition of donor elements in the A- and B-sites of the structure. In particular, the gadolinium (Gd3+) and niobium (Nb5+) ions will be used as modifiers on the perovskite structure by substitution of barium (Ba+2) and titanium (Ti+4) ions in the A- and B-site, respectively, considering the Ba1-xGdxTiO3 and BaTi1-x NbxO3 ( where x = 0.001, 0.002, 0.003, 0.004 and 0.005). The structural and microstructural properties were investigated at room temperature, while the electrical and dielectric properties were analyzed in a wide range of temperature and frequency. Particularly, the conductive effects provided by the doping with donor ions in different crystallographic sites, whose study has not yet been reported in the literature, were carefully investigated to better understand the factors that influence and determine the semiconductor properties of such materials. The objective is to enhance the understanding of the factors that influence and originate the conductive mechanisms in these materials at the microscopic and macroscopic level, therefore determining factors for a subsequent application in the electronics industry. The materials were obtained from the Pechini method (known as the Polymeric Precursors Method). This method is well known in the literature because it is a very efficient method, when compared with conventional methods for synthesis of polycrystalline materials, because of the numerous advantages it presents, such as the synthesis at low temperatures, low contamination, greater stoichiometric control, high homogenization and possibility of obtaining nanoscale powders.
Barium titanate (BaTiO3, BT) is a ferroelectric material with several applications for the electronic components market, due to its excellent physical properties when compared to other ferroelectric systems. So that, BT continues up today attracting the scientific and commercial interest for several decades. Among the large number of papers on the BT system reported in the literature, many are associated with the wide range of applications in the electric and electronic industry, where the use in capacitors, thermistors and other devices stands out. By doping BaTiO3 with donor ions implies in the change of some physical properties leading to abnormal behaviors in certain physical parameters. The nature of these changes is not yet very clear, although many papers have been reported trying to justify such effects. In this context, this work aims the investigation of the physical properties of the BaTiO3 system, considering the addition of donor elements in the A- and B-sites of the structure. In particular, the gadolinium (Gd3+) and niobium (Nb5+) ions will be used as modifiers on the perovskite structure by substitution of barium (Ba+2) and titanium (Ti+4) ions in the A- and B-site, respectively, considering the Ba1-xGdxTiO3 and BaTi1-x NbxO3 ( where x = 0.001, 0.002, 0.003, 0.004 and 0.005). The structural and microstructural properties were investigated at room temperature, while the electrical and dielectric properties were analyzed in a wide range of temperature and frequency. Particularly, the conductive effects provided by the doping with donor ions in different crystallographic sites, whose study has not yet been reported in the literature, were carefully investigated to better understand the factors that influence and determine the semiconductor properties of such materials. The objective is to enhance the understanding of the factors that influence and originate the conductive mechanisms in these materials at the microscopic and macroscopic level, therefore determining factors for a subsequent application in the electronics industry. The materials were obtained from the Pechini method (known as the Polymeric Precursors Method). This method is well known in the literature because it is a very efficient method, when compared with conventional methods for synthesis of polycrystalline materials, because of the numerous advantages it presents, such as the synthesis at low temperatures, low contamination, greater stoichiometric control, high homogenization and possibility of obtaining nanoscale powders.
Descrição
Palavras-chave
Materiais ferroelétricos, Titanato de bário, Terras-raras, Propriedades dielétricas, Condução, Ferroelectric materials, Barium titanate, Rare-earths, Dielectric properties, Conduction