The structural, magnetic and magnetoelectric properties were investigated for sol-gel prepared BaFeO nanorods and plate-like nanoparticles. Based on comparative experiments with bulk ceramics, it is found that larger structural distortion is present in nanostructures, which could cause the enhancement of magnetocrystalline anisotropy and the off-center displacement of Fe ions, and thus result in improved magnetic and magnetoelectric properties in BaFeO plate-like nanoparticles. Meanwhile, the local (Fe-Fe) dipoles, which usually appear during a high temperature sintering process, can also contribute to the negative magnetoelectric effect of BaFeO nanorods and a large room temperature magnetodielectric coefficient of about -13% is observed at 10 Hz and 9 kOe.
The relationship among dielectric anomaly, ferroelectric response, defects, and microstructures was established for (KNa)LiNbSbO (x = 0.04, 0.00, -0.02, -0.04 and -0.08) ceramics. For x = -0.02 and -0.04, larger coercive fields and lower remnant polarizations were obtained; besides, an additional dielectric relaxation behavior was observed with the activation energy E being about 2.19 eV and 1.92 eV, respectively. Furthermore, the grain and grain boundary contributions to the capacitance were separated using impedance spectroscopy, which, combined with back-scattering characterization, firmly indicates the core-shell structure of K-deficient samples (x = -0.02 and -0.04). Unlike the cores, the shells possess a large amount of K vacancies (). This work paves a way for regulating the fine structure and more on the electrical properties of KNN-based materials.
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