Banca de DEFESA: ALCINEY MIRANDA CABRAL

Uma banca de DEFESA de DOUTORADO foi cadastrada pelo programa.
DISCENTE : ALCINEY MIRANDA CABRAL
DATA : 20/06/2017
HORA: 14:00
LOCAL: Auditório do Química 3
TÍTULO:

SYNTHESIS BY COMBUSTION REACTION AND CHARACTERIZATION OF IRONPEROVSKITES La_xBi_1-xFeO₃ (x = 0.00, 0.10, 0.20 and 0.30), APPLIED TO MULTIFERROICS

PALAVRAS-CHAVES:

Perovskite, BiFeO_3, multiferroic, dieletrics and distorted antiferromagnetism

PÁGINAS: 197
GRANDE ÁREA: Ciências Exatas e da Terra
ÁREA: Química
SUBÁREA: Química Inorgânica
ESPECIALIDADE: Físico Química Inorgânica
RESUMO:

The multiferroics in single phase of the perovskite BiFeO₃ for La_xBi_1-xFeO₃ (x = 0.00, 0.10, 0.20 and 0.30) with the attributions BFO P.C., BFO700, BFO 830, L0.10BFO700, L0.20BFO700 and L0.30BFO700 were obtained by the method of adapted combustion reaction. The principal goal, this synthesis, is decrease the metastability of the BiFeO₃ in doping with La³⁺ in temperatures of sintering of 700 and 830^oC, influencing in their electrical and magnetic parameters. The materials formed were characterized by Rietveld refinement (DRX-Rietveld), Medium Infrared with Fourier transform (FTIR), Scanning Electron Microscopy with by Energy Dispersive Spectroscopy (SEM/EDS/ MAPPING), Thermal Analysis (TG/DTA) and Properties Magnetic and Electrical (VSM, ɛ’, ɛ’’ e tang δ). The preliminary results showed that the perovskite BiFeO₃, (BFO single phase) sinterized in temperatures at 700 ^oC (BFO/ Rhombohedral /R3c) and 830 ^oC (BFO/ Triclinic /P1) were directly dependent of the termic parameters. The dopagens by La³⁺ in the samples BFO700, L0.10BFO700, L0.20BFO700 and L0.30BFO700 presented different values of saturation magnetization, which resulted in different symmetries and space groups being the Rhombohedral/R3c - 0,011314 µB/[f.u.], Orthorhombic/Pnma - 0,006516 µB/[f.u.], Orthorhombic/Pbnm - 0,011503 µB/[f.u.] and Orthorhombic/Pbnm - 0,009509 µB/[f.u.]), respectively. The analysis by FTIR/DRX-Rietveld showed the strong vibrations (530.34; 531.61; 551.51cm^-1) attributed to octahedral stretch for perovskite (BiFeO₃) that is a characteristic of the FeO₆ geometries, related to distorted antiferromagnetic structures. The dielectricity of ceramics is greater than 6 and the tangent of losses smaller than -0.13 in range 0 – 0.5 GHz. The quality factor was measured and all were smaller than -10 the -25dB. These results of chemical substrates shows that the investigated ceramics can be applied to multiferroics antenna.

MEMBROS DA BANCA:
Presidente - 350633 - ADEMIR OLIVEIRA DA SILVA
Interno - 1959889 - DAVI SERRADELLA VIEIRA
Externo ao Programa - 338292 - JOAO BOSCO LUCENA DE OLIVEIRA
Externo à Instituição - MARCOS TAVARES DE MELO - UFPE
Externo ao Programa - 345799 - OTOM ANSELMO DE OLIVEIRA
Externo à Instituição - ULISANDRA RIBEIRO DE LIMA - IFRN