"Fe2-xCrxO3氧化物之奈米微粒介電性質研究(x = 0, 0.3, 0.7,1, and 2)"

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The synthesis, characterization and dielectric properties of Corundum Fe2-xCrxO3 (x = 0, 0.3, 0.7, 1, and 2) nanoparticles were investigated. These nanoparticles were synthesized by co-precipitation method. The resulting X-ray diffraction patterns show that all these nanoparticles are single phase corundum structure. The average particle sizes were found to vary from ~ 30 nm to ~ 120 nm with increasing annealing temperature from 500 oC to 1000 oC. At room temperature, the real part of dielectric permittivity e'(T) increases with increasing particle size in all compositions except for x = 2. The corresponding loss tangent tanD(T) curves exhibits maxima. These peak positions shift to higher temperature as the measuring frequency increases, indicating thermally activated relaxation process. Complex modulus analysis was used to distinguish the grain and grain boundary contribution to these nanoparticles. The results suggest that the dominance of grain boundary resistance at room temperature in all compositions. So far, the discovery in this thesis may provide a better understanding of the dielectric properties of the antiferromagnetic Fe2-xCrxO3 system to other researchers. It might be even extended to other antiferromagnetc compounds and their applications.