Avaliação da dinâmica de portadores de carga em cerâmica multiferróicas por meio de espectroscopia dialétrica

Detalhes bibliográficos
Ano de defesa: 2015
Autor(a) principal: Silveira, Luiz Gustavo Davanse da
Orientador(a): Não Informado pela instituição
Banca de defesa: Não Informado pela instituição
Tipo de documento: Tese
Tipo de acesso: Acesso aberto
Idioma: por
Instituição de defesa: Universidade Estadual de Maringá
Brasil
UEM
Maringá, PR
Programa de Pós-Graduação em Física
Programa de Pós-Graduação: Não Informado pela instituição
Departamento: Não Informado pela instituição
País: Não Informado pela instituição
Palavras-chave em Português:
Link de acesso: http://repositorio.uem.br:8080/jspui/handle/1/2602
Resumo: In this work, temperature-dependent and frequency-dependent dielectric investigations have been performed in TbMnO3 ceramics processed in either oxygen or argon atmospheres The dieletric constant of both samples exhibited three anomalies in the temperature range between 12 and 300 K. Two anomalies occurred above 100 K and were atributed to the Maxwell-Wagner effect in grain boundaries and to hopping polarization in grain cores. Also, a strong correlation between dielectric properties and crystalline structure was observed. In the sample processed in oxygen atmosphere, the presence of manganese vacancies and the smaller unit cell allow the long range motion of charge carriers. In the sample processed in argon atmosphere, on the other hand, charge carriers have only short range motion. Also, in this sample the existance of inequivalent hopping probabilities was observed, which are a result of intrinsic factors like orbital ordering, bondig anisotropies, and Hund interaction Bellow 100 K a dielectric relaxation was observed. This relaxation follows the empirical Cole-Cole model and was attributed to small polaron tunnelling. X-ray photoelectrons spectroscopy was also conducted. The results showed that indeed the structural differences resulted in diferences between the electronic structure of the samples.