Effect of the CoFe2O4 initial particle size when sintered by microwave on the microstructural, dielectric, and magnetic properties

摘要

Abstract 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.