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Effect of the CoFe 2 O 4 initial particle size when sintered by microwave on the microstructural, dielectric, and magnetic properties
Author(s) -
Fernández Perdomo Claudia P.,
Zabotto Fabio L.,
Garcia Ducinei,
Kiminami Ruth H. G. A.
Publication year - 2019
Publication title -
international journal of applied ceramic technology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.4
H-Index - 57
eISSN - 1744-7402
pISSN - 1546-542X
DOI - 10.1111/ijac.13200
Subject(s) - materials science , particle size , dielectric , sintering , grain size , microstructure , dielectric loss , particle size distribution , dissipation factor , particle (ecology) , microwave , grain growth , composite material , magnetization , nanoparticle , magnetic field , nanotechnology , optoelectronics , chemical engineering , oceanography , physics , quantum mechanics , engineering , geology
The particle size of CoFe 2 O 4 powders (average particle size of 350 nm) was reduced to 50 nm by high‐energy milling. In this paper, special attention was given for analyzing the densification and grain growth of both particle sizes (350 and 50 nm) subject to ultrafast sintering assays using microwave sintering and their effect on the magnetic and electric properties. The results indicated that the grain growth was 10 times higher for the nanoparticle system, reaching similar sizes of ~1 μm in both cases after sintering. The relative density values were higher (95%) in the nanoparticle system due to the wide distribution of particle sizes generated in the grinding process. Qualitatively inferred microscopy analysis showed high sinterability of fine particles with a narrow distribution of grain size when subjected to ultrafast firing processes. Magnetization measurements at room temperature clearly show the reduction of Hc with increasing grain size. Electric resistivity, dielectric constant ( ε ′), and dielectric loss tangent (tan δ ) were measured as a function of frequency at room temperature. The low values of dielectric constant ( ε ′) and dielectric loss (tan δ ) in the low frequency range, shown for all samples sintered by microwave, prove the excellent uniformity in the microstructure.