Teses de doutorado

URI Permanente para esta coleção

http://repositorio.ufes.br/handle/10/12247

Navegar

Navegando Teses de doutorado por Autor "Aguiar, Jose Albino Oliveira de"

Agora exibindo 1 - 1 de 1
  • Nenhuma Miniatura disponível
    Item
    Síntese e caracterização elétrica do composto ferroelétrico PZT 52/48 dopado com érbio
    (Universidade Federal do Espírito Santo, 2019-12-12) Caceres, Jaime Alberto Sanchez; Passos, Carlos Augusto Cardoso; https://orcid.org/0000-0001-9627-7941; http://lattes.cnpq.br/2528679879816545; https://orcid.org/0000-0001-9553-1776; http://lattes.cnpq.br/2773300928152977; Franco Junior, Adonias Ribeiro ; https://orcid.org/; http://lattes.cnpq.br/6677652514776940; Aguiar, Jose Albino Oliveira de; https://orcid.org/0000-0002-2040-2301; http://lattes.cnpq.br/5602764549201959; Orlando, Marcos Tadeu D Azeredo; https://orcid.org/0000000283876504; http://lattes.cnpq.br/3562894103432242; Passamai Junior, Jose Luis ; Vieira, Estefano Aparecido
    In this work, erbium-doped PZT 52/48 ceramics at sites A and B were prepared by the Pechini method for the purpose of studying their dielectric properties. Specifically, the dielectric anomalies of interfacial origin in these ferroelectrics were investigated. To determine the best sintering/densification temperature of ceramic samples, dilatometry tests were performed. These results of the tests showed that the ceramic samples presented relative densities above 95%. The samples were characterized by X-ray diffraction. The results indicated that all samples are single phase and the peaks are indexed to the tetragonal crystal structure. According to these results, there was also an increase of the parameter “a” and a reduction of the parameter “c” in relation to the undoped DZT sample. Through scanning electron microscopy, it was observed that average grain size decreased with increasing erbium content. All samples were subjected to electrical measurement analysis. The dielectric response of the grains showed characteristics of materials that follow Curie-Weiss law, typical of ferroelectrics. On the other hand, the dielectric anomaly phenomenon was observed for the responses of these materials at high temperatures and low frequencies. Impedance spectroscopy analyzes by equivalent circuit (brick-layer model) revealed a predominance of dielectric properties of intergranular interfaces as the cause of this anomaly. It was considered the layer model (grain and grain boundary) in series. The electrical characterization of our ceramics showed a peculiar ferroelectric-paraelectric phase transition around 390 °C. In addition, measurements of ferroelectric hysteresis for doped samples at sites A and B revealed that remnant polarization and coercive field values depend on erbium concentration and PbO losses. The undoped sample showed higher values of permittivity compared to erbium doped samples at both sites A and B.