Abstract
Al3+-Co2+ co-substituted M-type SrCaNd hexaferrites with cation compositions Sr0.5Ca0.2Nd0.3Fe12.0-x(Al0.5Co0.5)xO19 were synthesized using the traditional ceramic process by varying AlCo content (x) (0.0 ≤ x ≤ 0.5). The microstructures, morphologies and ferromagnetic properties of the samples were investigated as a function of AlCo content (x) by X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), Fourier transformer infrared (FT-IR) spectroscopy and Hysteresis graph meter. The X-ray diffraction patterns show that the hexaferrites with AlCo content (x) of 0.0 ≤ x ≤ 0.2) exhibited M-type phase and α-Fe2O3 as impurity phase, while the hexaferrites with AlCo content (x) ≥ 0.3 exhibited the single M-type phase. XRD, along with FT-IR analysis confirmed the formation of M-type hexaferrites and the successful substitution of Al3+ and Co2+ ions in the hexaferrite lattice. The results of FE-SEM images proposed that all the particles with regular hexagonal platelet-like shape were homogeneous dispersed. The remanence (Br) first increased with AlCo content (x) from 0.0 to 0.3, and then decreased when AlCo content (x) ≥ 0.3. The intrinsic coercivity (Hcj) and magnetic induction coercivity (Hcb) first increased with AlCo content (x) from 0.0 to 0.2, and then decreased with AlCo content (x) from 0.2 to 0.3, and increased when AlCo content (x) ≥ 0.3. Maximum energy product [(BH)max] first increased with AlCo content (x) from 0.0 to 0.2, and then decreased at AlCo content (x) ≥ 0.2. Squareness ratio (Hk/Hcj) decreased with increasing AlCo content (x) from 0.0 to 0.5.
Highlights
The M-type hexaferrites (AFe12O19, A = Sr, Ba and Pb) are ferrimagnets consisting of five crystallographically inequivalent sublattices of Fe3+ ions, such as three octahedral positions (12k, 4f2 and 2a), one tetrahedral position (4f1), and one trigonal bipyramidal positions (2b)
XRD, FE-SEM, and Fourier transformer infrared (FT-IR) were used to investigate the micro-structural of the samples
The results of FE-SEM images proposed that all the particles with regular hexagonal platelet-like shape were homogeneous dispersed and the average particles basically kept unchanged with the increase of AlCo content (x)
Summary
The M-type hexaferrites (AFe12O19, A = Sr, Ba and Pb) are ferrimagnets consisting of five crystallographically inequivalent sublattices of Fe3+ ions, such as three octahedral positions (12k, 4f2 and 2a), one tetrahedral position (4f1), and one trigonal bipyramidal positions (2b). The 2a, 2b and 12k positions are spin up, but the 4f1 and 4f2 positions are spin down.[1] M-type hexaferrites have attracted considerable attention because of their perfect chemical stability, high saturation magnetization, high Curie temperature, high coercivity, and high performance-price ratio.[2,3] And they have been widely used in various technological applications in permanent magnets, microwave devices and recording media.[4,5] The low price of M-type hexaferrites and easy manufacturing extremely enhanced their production and commercial effectiveness. In order to meet the needs of the market, a number of studies have been devoted to enhance the magnetic properties of M-type hexaferrites.
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