Multiferroic nanoparticles of Bi 1-x Ba x FeO 3 (BiBaFeO 3 ); (x = 0.10, 0.15, 0.20 and 0.25 mol%) samples were prepared using conventional solid-state method. The nanostructural and transport properties of the prepared samples were investigated by X-ray diffraction (XRD), scanning electron microscope (SEM) and electrical conductivity. XRD patterns show the formation of BiBaFeO 3 with single-phase rhombohedral-hexagonal structure. The particles sizes were found to be in the range 20-33 nm. SEM micrograph revealed the nanostructure consisting of small, randomly oriented and non-uniform grains. Dc conductivity shows that all samples are semiconductor and the maximum was found at x = 0.15 mol%. This increase of the conductivity can be attributed to the decrease in grain boundary scattering due to the reduction in crystallite size. The calculated activation energy for the multiferroic nanoparticles was found to be 0.413-0.929 eV. The conduction was confirmed to obey non-adiabatic small polaron hopping (SPH). The electron-phonon interaction coefficient (c p ) was calculated and found to be in the range of (12.79-27.21). The hopping carrier mobility varied from 1.85 9 10 -7 cm 2 V -1 s -1 to 8.01 9 10 -13 cm 2 V -1 s -1 at 418 K. The conductivity was primarily determined by hopping carrier mobility.
Ferroelectric samples Sr1−xBaxTiO3 (BST), where x = 0, 0.2, 0.4, 0.6, 0.8 and 1, were prepared using the tartrate precursor method and annealed at 1200 °C for 2 h. X-ray diffraction, “XRD”, pattern analysis verified the structure phase. The crystallite size of the SrTiO3 phase was calculated to be 83.6 nm, and for the TiO2 phase it was 72.25 nm. The TEM images showed that the crystallites were agglomerated, due to their nanosize nature. The AC resistivity was measured as temperature dependence with different frequencies 1 kHz and 10 kHz. The resistivity was decreased by raising the frequency. The dielectric properties were measured as the temperature dependence at two frequencies, 1 kHz and 10 kHz. The maximum amount of dielectric constant corresponded to the Curie temperature and the transformation from ferroelectric to paraelectric at 1 kHz was sharp at 10 kHz. Polarization–electric field hysteresis loops for BST samples were measured using a Sawer–Tawer modified circuit. It was shown that the polarization decreased with increasing temperature for all samples.
A Series of ferrite samples Ni0.1 Cu0.2 Zn0.7-x Mgx Fe2O4 (where x = 0, 0.15, 0.25, 0.35, 0.45, 0.55 and 0.7) were synthesized using auto combustion flash method. The samples were annealed at 600 °c for 2 hours to eliminate the foreign phases of the constituent nitrate and internal stress. The purity of phase structure was confirmed by x-ray diffraction. Some structural and microstructural parameters like porosity, x-ray density, crystallite size and lattice constant were deduced from x-ray. Scanning electron microscope (SEM) analysis reveals that the grains are separated by pores in all samples and the average grain size decreases with increasing Mg content. Magnetic properties such as coercivity (Hc), saturation magnetization (Ms) and retentivity (Mr) were measured from M-H loops. The magnetization curves were characterized by low coercivity indicating that our samples are soft magnetic material. Both saturation magnetization and coercivity increase by increasing Mg ions where Ms reaches maximum value at x = 0.35 then decrease for higher Mg content.
Using the auto combustion flash method, Ni1−x+2Mgx+2Fe2+3O4 (x = 0, 0.2, 0.6, 0.8 and 1) nano-ferrites were synthesized. All samples were thermally treated at 973 K for 3 h. The structural analysis for the synthesized samples was performed using XRD, high-resolution transmission electron microscopy (HRTEM), and FTIR. Scanning electron microscopy (SEM) was undertaken to explore the surface morphology of all the samples. The thermal stability of these samples was investigated using thermogravimetric analysis (TGA). XRD data show the presence of a single spinel phase for all the prepared samples. The intensity of the principal peak of the spinel phase decreases as Mg content increases, showing that Mg delays crystallinity. The Mg content raised the average grain size (D) from 0.084 μm to 0.1365 μm. TGA shows two stages of weight loss variation. The vibrating sample magnetometer (VSM) measurement shows that magnetic parameters, such as initial permeability (μi) and saturation magnetization (Ms), decay with rising Mg content. The permeability and magnetic anisotropy at different frequencies and temperatures were studied to show the samples’ magnetic behavior and determine the Curie temperature (TC), which depends on the internal structure. The electrical resistivity behavior shows the semi-conductivity trend of the samples. Finally, the dielectric constant increases sharply at high temperatures, explained by the increased mobility of charge carriers, and decreases with increasing frequency.
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