Investigação das propriedades físicas das hexaferritas de bário e estrôncio dopadas com íon de Ce3+ e Gd3+

• Ano de defesa: 2015
• Autor(a) principal: Andrade, Bruna da Costa
• Orientador(a): Macêdo, Marcelo Andrade
• Tipo de documento: Tese
• 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: Hexaferrita; Propriedades físicas; Gadolínio; Cério
• Palavras-chave em Inglês: Hexaferrite; Physical properties; Gadolinium; Cerium
• Área do conhecimento CNPq: CNPQ::CIENCIAS EXATAS E DA TERRA::FISICA
• Link de acesso: https://ri.ufs.br/handle/riufs/5257

Hexaferrites have a broad scope for application based on their physical properties. To study the influence of replacing cerium and gadolinium ions in hexaferrites, it is very important to understand their structural, electrical, and magnetic properties of hexaferrites. In this regard, the W-type strontium hexaferrite doped with Ce3 + and Gd3+ ions was prepared using a proteic sol-gel process under a pressure of 3000 psi and sintered at 1200º C for 2 h at a heating rate of 1 and 2º C/min. A pure W-type strontium hexaferrite was identified using X-ray diffraction (XRD); the XRD patterns exhibited increasing lattice parameters and unit cell volume as a function of doping. Scanning electron microscopy analysis indicated growth on plates with hexagonal divisions. The inserted Gd3+ and Ce3+ ions caused imbalance in the lattice. Therefore, some of the Fe3+ ions present in the octahedral site were converted to Fe2+ ions. Thus, the Curie temperature was reduced to 474º C, increasing the coercivity and reducing the superexchange interactions between Fe-O. The high saturation magnetization and low coercivity in the samples indicate that the hexaferrites are potential candidates for applications involving microwave absorption. In addition, impedance spectroscopy measurements indicated the presence of a replacement threshold with rare earth ions, which results in an increased resistivity; this is predominantly mediated by oxygen vacancies in the Ce3+-doped hexaferrite.