A-Site Cation Size Effect on Structure and Magnetic Properties of Sm(Eu,Gd)CrMnFeCoNiO High-Entropy Solid Solutions.

Three high-entropy Sm(Eu,Gd)CrMnFeCoNiO perovskite solid solutions were synthesized using the usual ceramic technology. The XRD investigation at room temperature established a single-phase perovskite product. The Rietveld refinement with the FullProf computer program in the frame of the orthorhombic Pnma (No 62) space group was realized.

Polysubstituted High-Entropy [LaNd](CrMnFeCoNi)O Perovskites: Correlation of the Electrical and Magnetic Properties.

La-, Nd- and La/Nd-based polysubstituted high-entropy oxides (HEOs) were produced by solid-state reactions. Composition of the B-site was fixed for all samples (CrMnFeCoNi) with varying of A-site cation (La, Nd and LaNd). Nominal chemical composition of the HEOs correlates well with initial calculated stoichiometry.

High Entropy Oxide Phases with Perovskite Structure.

The possibility of the formation of high entropy single-phase perovskites using solid-state sintering was investigated. The BaO-SrO-CaO-MgO-PbO-TiO, BaO-SrO-CaO-MgO-PbO-FeO and NaO-KO-CaO-LaO-CeO-TiO oxide systems were investigated. The optimal synthesis temperature is found between 1150 and 1400 °C, at which the microcrystalline single phase with perovskite structure was produced.

Extremely Polysubstituted Magnetic Material Based on Magnetoplumbite with a Hexagonal Structure: Synthesis, Structure, Properties, Prospects.

Crystalline high-entropy single-phase products with a magnetoplumbite structure with grains in the μm range were obtained using solid-state sintering. The synthesis temperature was up to 1400 °C. The morphology, chemical composition, crystal structure, magnetic, and electrodynamic properties were studied and compared with pure barium hexaferrite BaFeO matrix.

Magnetic and Structural Properties of Barium Hexaferrite BaFeO from Various Growth Techniques.

Barium hexaferrite powder samples with grains in the μm-range were obtained from solid-state sintering, and crystals with sizes up to 5 mm grown from PbO, Na₂CO₃, and BaB₂O₄ fluxes, respectively. Carbonate and borate fluxes provide the largest and structurally best crystals at significantly lower growth temperatures of 1533 K compared to flux-free synthesis (1623 K). The maximum synthesis temperature can be further reduced by the application of PbO-containing fluxes (down to 1223 K upon use of 80 at % PbO), however, Pb-substituted crystals BaPbFeO with Pb contents in the range of 0.

Three Oxidation States of Manganese in the Barium Hexaferrite BaFeMnO.

The coexistence of three valence states of Mn ions, namely, +2, +3, and +4, in substituted magnetoplumbite-type BaFeMnO was observed by soft X-ray absorption spectroscopy at the Mn-L edge. We infer that the occurrence of multiple valence states of Mn situated in the pristine purely iron(III) compound BaFeO is made possible by the fact that the charge disproportionation of Mn into Mn and Mn requires less energy than that of Fe into Fe and Fe, related to the smaller effective Coulomb interaction of Mn (d) compared to Fe (d). The different chemical environments determine the location of the differently charged ions: with Mn occupying positions with (distorted) octahedral local symmetry, Mn ions prefer octahedrally coordinated sites in order to optimize their covalent bonding.