Structural and magnetic properties of La-doped strontium-hexaferrites ceramics obtained by spark-plasma sintering

• Published in: Journal of magnetism and magnetic materials 2021-09, Vol.533, p.167966, Article 167966
• Main Authors: Govea-Alcaide, E., Matilla-Arias, J., Guerrero, F., Mariño-Castellanos, P., Montero-Rey, K., Rosales-Saiz, F., Machado, I.F.
• Format: Article
• Language: English
• Subjects: Coercivity; Diffraction patterns; Finite element method; La-doped Strontium hexaferrite; Magnetic properties; Magnetic saturation; Magnetization; Particle size distribution; Phases; Plasma sintering; Rietveld method; Room temperature; Sintering (powder metallurgy); Spark plasma sintering; Structural and magnetic properties; X ray powder diffraction
• ISSN: 0304-8853; 1873-4766
• DOI: 10.1016/j.jmmm.2021.167966

•Sr1-xLaxFe12O19 (x = 0.1, 0.3, and 0.6) hexaferrite were successfully obtained by spark-plasma sintering (SPS) from as-calcined powders.•Finite element simulation of the SPS process.•Rietveld refinement of the samples obtained under SPS condition and with different La-content.•The Sr1-xLaxFe12O19 is dominant phase and the contribution of secondary phases does not reduce the coercivity of the system.•First-order reversal curves (FORC) revealed details of the magnetic behavior of the samples. Polycrystalline samples of Sr1−xLaxFe12O19 (x = 0.1, 0.3, and 0.6) hexaferrite were prepared by spark-plasma sintering (SPS) and its structural and magnetic properties have been investigated. The SPS process were performed under vacuum, at 900 °C, and in only 5 min. X-ray powder diffraction patterns showed that before SPS sintering samples are composed by several phases where the SrFe12O19 (SrM) is not higher than 12%. From Rietveld refinement method, we have found that after SPS process the content of SrM phase increased, in mean, up to 68%. However, it was found the presence of secondary phase such as α-Fe2O3 and LaFeO3 (%) whose phase content also vary with increasing the La-content. A finite element simulation model were used to study the temperature evolution within the sample during the SPS treatment. Magnetization measurements at room temperature yielded values of saturation magnetization between ~43 to ~27 emu/g and coercivities, HcB, in the range 3.11 to 2.88 kOe with increasing x. The influence and possible interaction between detected magnetic phases was studied by means of first-order reversal curves (FORCs) measurements. Results indicated that magnetic behavior of the La-doped strontium hexaferrites obtained by SPS technique are analogous a system composed of a broad distribution particles that are exchange-coupled with a certain number of other of neighboring particles. From FORC maps the coercivity profiles of the studied samples were extracted. The asymmetric behavior of these profiles were related to a broad distribution of the particle size and/or the influence of the secondary magnetic phases.