부산대학교 도서관

In this work, composites were prepared from La–Co-doped strontium ferrite (SrFe12O19) and soft magnetite (Fe3O4) in a 1:5 weight ratio, spanning a range of substitutions from z = 0.0 to 0.5. The X-ray diffraction analysis of all prepared composites revealed the co-existence of hard (M-type) and soft (spinel) ferrite phases. Notably, in z = 0.0 (20% Fe3O4 of SrFe12O19) a minor trace of α -Fe2O4 was observed. Field emission scanning electron microscopy (FESEM) micrographs displayed distinct particles of M-type and spinel ferrite at z = 0.0, and substitution rendered a change in grain/grain size distribution. Composition z = 0.4 exhibited the highest dielectric constant, which can be correlated with the maximum grain boundary capacitance Cgb (29.77 μ F ) calculated from impedance spectroscopy software. In contrast, z = 0.3 revealed the maximum conductivity relaxation and explained through the dense/closely packed grains observed in micrographs. The replacement of Fe3+ ions with Co–La ions caused a reduction in conductivity value and was maximum for z = 0.4 (3.26 × 10–5 Ω−1 m−1) in the high-frequency region. A segment of a semicircular arc had been observed in all synthesized composites in Z ″ vs. Z ′ Cole–Cole plots. This observation indicated a significant enhancement in dielectric relaxation brought about by the Co–La substitution. [ABSTRACT FROM AUTHOR]