Estudos das propriedades estruturais do composto BiFeO3 via difração de raios X de alta resolução e cálculos de densidade eletrônica

• Ano de defesa: 2012
• Autor(a) principal: Catellani, Igor Barbosa
• Tipo de documento: Dissertação
• Tipo de acesso: Acesso aberto
• Idioma: por
• Instituição de defesa: Universidade Estadual de Maringá; Brasil; Programa de Pós-Graduação em Física; UEM; Maringá, PR; Centro de Ciências Exatas
• Palavras-chave em Português: Multiferróico; Densidade eletrônica; Sincroton; Ferroelétrica; Brasil.; Ciências Exatas e da Terra; Física
• Link de acesso: http://repositorio.uem.br:8080/jspui/handle/1/2693

Multiferroic materials have attracted much attention in the academic and business due to their application possibilities and challenges in the field of basic science. Among the multiferroics, BiFeO3 stands out due to its ferroelectric and antiferromagnetic transitions at high temperatures. Despite of having hundreds of articles published in recent years on the BiFeO3, the results regarding the crystal structure of this material are still quite conflicting. In this work, a study was conducted to describe the crystal structure of BiFeO3. For this we used two samples prepared by different routes: high-energy ball milling and sol-gel method. High resolution X-ray diffraction patterns were obtained for both samples at X-ray powder diffraction beam line XPD line of the Brasilian Synchrotron Light Laboratory, Brazil. We performed a systematic study on the most stable structure for BiFeO3 testing various space groups. From these fits were obtained structural models using symmetries rhombohedral (space group R3c), monoclinic (space group Cc) and a model of coexistence of the two phases. With these models, structural refinements were performed by using the Rietveld method. The refinements had used two models for the atomic displacement factor: isotropic and anisotropic. By analyzing the achieved results, we confirmed that the compound BiFeO3 can be described by the monoclinic space group Cc or at least by the coexistence of R3c and Cc space groups. Further, our work is the first study to describe full crystallographic details of the monoclinic symmetry Cc for BiFeO3 compound. Finally, we performed an analysis of how the electronic densities are modified using the three models by applying the maximum entropy method.