Banca de DEFESA: EMANOEL LAURERTAN TAVARES FRANÇA

Uma banca de DEFESA de DOUTORADO foi cadastrada pelo programa.
STUDENT : EMANOEL LAURERTAN TAVARES FRANÇA
DATE: 24/05/2022
TIME: 14:00
LOCAL: Programa de Pós-Graduação em Ciência de Materiais
TITLE:
KEY WORDS:

ceramics; solid state reaction; NBT; rare-earth.

PAGES: 115
BIG AREA: Outra
AREA: Multidisciplinar
SUMMARY:

In this work, ceramics samples of de Na0.5Bi0.5-𝑥A𝑥TiO3 and Na0.5Bi0.5Ti1-𝑥Fe𝑥O3 (A = Fe, Nd e Yb and 𝑥 = 0, 0.5, 1.0, 1.5 and 2.0 were prepared by a solid-state reaction technique. The influence of the addition of magnetic ions in the structural, electrical and magnetic properties was investigated by using X-ray diffraction (XRD), Raman spectroscopy, magnetization and electrical permittivity measurements. From the treatment of X-ray diffraction data, it was possible to obtain information on the crystal structure, and it was found that it is of the perovskite type, trigonal, belonging to the R3c space group. The Raman spectra were duly associated with the vibrational and rotational modes typical of this crystal structure and which suffer distortions with the addition of doping elements. The magnetic property was investigated by measuring hysteresis loops and ac and dc magnetic susceptibility by using a PPMS (Physical Property Measurement System – Quantum Design). A paramagnetic behavior was induced in the diamagnetic NBT by the addition of the replacement of Bi and Ti by the magnetic ions. The Curie-Weiss law was used to obtain the average values for the magnetic moment of the doping ions by using the dc magnetization data obtained in the temperature range 5 – 300 K, obtaining effective magnetic moment values for the compounds doped with rare earth metals on average 4.78 and 3.72 𝜇B for the Nd and Yb ions respectively. The electrical impedance was measured for frequencies varying from 20 Hz to 2.0 GHz. It was observed an enhancement in the values for the dielectric constants. In particular, a value larger than 103 was obtained for a Yb-doped sample (x = 0.020). The overall dialectic losses were found to be quite small. The dependence of the permittivity with the frequency was properly account for by using the Cole-Davidson.

BANKING MEMBERS:
Externa à Instituição - LUZELI MOREIRA DA SILVA - UFMA
Externo à Instituição - ADOLFO FRANCO JUNIOR - UFG
Interno - 1806089 - EDUARDO HENRIQUE LAGO FALCAO
Interno - 2457389 - EDUARDO PADRON HERNANDEZ
Presidente - 1133626 - FERNANDO LUIS DE ARAUJO MACHADO