Síntese e caracterização estrutural, dielétrica e magnética dos compósitos cerâmicos multifuncionais (1-x)K0,5Na0,5Nb0,7Ta0,3O3- xCoFe2O4 (0≤x≤0,3)
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2016-12-22
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Universidade Federal de Goiás
Resumo
Lead-free multifunction composites are of great interest to the scientific community
as they have several potential applications. Such composites were produced from the ferroelectric
compound free of lead niobate and potassium sodium tantalate (KNNT) and the
magnetic nanoparticles of cobalt ferrite (CFO). A particulate composite was then produced
with the ferroelectric matrix and magnetic nanoparticles. First, the influence of the sintering
temperature (950 and 1100 °C) on the ceramic densification process was investigated.
Ceramics sintered at 950 °C showed very low density, unlike those sintered at 1100 °C, which
have a density of 90%. The microstructure of the composites and how the magnetic particles
are distributed in the matrix were investigated. The composites presented the perovskite,
spinel and tungsten bronze structural phases; The lattice constant of all crystalline phases
remained constant, so there was no migration of cations between the distinct phases. The
value of the relative dielectric constant of the pure KNNT is 700, which is comparable to
the values found in the literature. In the composites, the dielectric constant value decreases
coherently with the amount of cobalt ferrite. The coercivity of the nanoparticles before and
after the sintering is 1494 and 675 Oe, respectively, in the composites the value of coercivity
remains constant. On the other hand, the saturation magnetization of nanoparticles before
and after sintering is 63 and 68 emu/g, respectively. The value of the saturation magnetization
reduces coherently with the amount of ferrite present in the other composites. In this
way, it was shown that the electrical and magnetic properties coexist in the composite, since
the magnetic properties depend exclusively on the cobalt ferrite.
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KNNT , CFO , Magnetismo , Constante dielétrica , Compósito , KNNT , CFO , Magnetism , Dieletric constant , Composite
Citação
CARVALHO, F. M. Síntese e caracterização estrutural, dielétrica e magnética dos compósitos cerâmicos multifuncionais (1-x)K0,5Na0,5Nb0,7Ta0,3O3- xCoFe2O4 (0≤x≤0,3). 2016. 59 f. Dissertação (Mestrado em Fisica) - Universidade Federal de Goiás, Goiânia, 2016.