Caracterização de materiais cerâmicos multiferróicos de composição PFN e PFW por espectroscopia de absorção de raios X

• Autor(a) principal: Andrade Junior, Nelson Moreira de [UNESP]
• Data de Publicação: 2017
• Tipo de documento: Trabalho de conclusão de curso
• Idioma: por
• Título da fonte: Repositório Institucional da UNESP
• Texto Completo: http://hdl.handle.net/11449/156905; http://www.athena.biblioteca.unesp.br/exlibris/bd/capelo/2018-08-31/000905693.pdf
• topic: Ciência dos materiais; Material cerâmico; Espectroscopia de raio X

The continuous and increasing demand for electronic devices, with high performance, greater versatility and miniaturized has accentuated the interest no study and development of new materiais (monophasic or composite), that integrate two or more physical properties of strong technological interest. Materiais with these characteristics have more recently been called multifunctional materiais or active / intelligent materiais, such as multiferroic materiais. The term multiferroic was created to refer to materiais which simultaneously exhibit a coexistence of at least two ferric properties. Examples of multiferroic materiais are compounds Pb(Fe112Nb112)O3 (PFN), Pb (Fe213W113)Q3 (PFW). There is still a long-distance structure and as electrical / magnetic properties, such as have been characterized by numerous researchers with a better purpose in phase transition processes and electric behavior of these compounds, works carried out with the objective of verifying the existence of a correlation between these properties and a local order and electronic structure of materiais. ln this work, short range order of PFN and PFW composition ceramics were characterized by the technique of X-ray absorption spectroscopy at the edges K of Fe and L111 of Pb as a function of temperature. The investigations of the EXAFS spectra on the edges K of Fe show that for a PFN structure for temperatures 400 K, 500 K, 550 K and 600 K the best symmetry that it describes is the Tetragonal, at the edge LIII of the Pb the best symmetry is the rhombohedron for all temperatures investigated. As the analyzes performed for the PFW showed a better local structure and described by Cubic symmetry at the temperatures 450 K and 600 K, which does not occur for the temperatures 500 K and 550 K that presents as best symmetry to Rhombohedral for atoms to the around the LIII border. The most symmetrical symmetry is a Rhombohedral...