A-Site Cation Size Effect on Structure and Magnetic Properties of Sm(Eu,Gd)Cr0.2Mn0.2Fe0.2Co0.2Ni0.2O3 High-Entropy Solid Solutions

Abstract

Three high-entropy Sm(Eu,Gd)Cr0.2Mn0.2Fe0.2Co0.2Ni0.2O3 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. Along with a decrease in the V unit cell volume from ~224.33 Å3 for the Sm-based sample down to ~221.52 Å3 for the Gd-based sample, an opposite tendency was observed for the unit cell parameters as the ordinal number of the rare-earth cation increased. The average grain size was in the range of 5–8 μm. Field magnetization was measured up to 30 kOe at 50 K and 300 K. The law of approach to saturation was used to determine the Ms spontaneous magnetization that nonlinearly increased from ~1.89 emu/g (Sm) up to ~17.49 emu/g (Gd) and from ~0.59 emu/g (Sm) up to ~3.16 emu/g (Gd) at 50 K and 300 K, respectively. The Mr residual magnetization and Hc coercive force were also determined, while the SQR loop squareness, k magnetic crystallographic anisotropy coefficient, and Ha anisotropy field were calculated. Temperature magnetization was measured in a field of 30 kOe. ZFC and FC magnetization curves were fixed in a field of 100 Oe. It was discovered that the Tmo magnetic ordering temperature downward-curve decreased from ~137.98 K (Sm) down to ~133.99 K (Gd). The spin glass state with ferromagnetic nanoinclusions for all the samples was observed. The <D> average and Dmax maximum diameter of ferromagnetic nanoinclusions were calculated and they were in the range of 40–50 nm and 160–180 nm, respectively. The mechanism of magnetic state formation is discussed in terms of the effects of the A-site cation size and B-site poly-substitution on the indirect superexchange interactions.

High-entropy materials for thermoelectric applications: towards performance and reliability

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High-Entropy Hexagonal Manganites for Fast Oxygen Absorption and Release

“…High-entropy chemical compositions are a rapidly emerging approach to design functional oxides. Following early studies of mechanical properties of metal alloys with 5 or more elements in single-phase solid solution, , high entropy has later been explored for oxides and ceramics, − e.g., rock salts, perovskites, , oxyfluorides, and carbides . High-entropy compounds are usually defined by having a configurational entropy, S config , larger than 1.5 R , where R is the universal gas constant, which is achieved by 5 or more equimolar elements on the same sublattice .…”

A review on high entropy silicides and silicates: Fundamental aspects, synthesis, properties

“…High entropy oxides are entropy‐stabilized, configurationally disordered oxides with a maximal configurational entropy of mixing. Inspired by the display of unanticipated properties of high entropy oxides, the ceramic community introduced high entropy in non‐oxide ceramic systems 14,15 . As the timeline Figure 1 shows, high entropy borides were discovered in 2016, 16 followed by high entropy nitrides, carbides, and sulfides in 2018, 17–19 high entropy fluorides, silicides and silicates in 2019, 7,9,20 high entropy layered hydroxides in 2020, 21 and high entropy MXene in 2022 22 .…”

“…Inspired by the display of unanticipated properties of high entropy oxides, the ceramic community introduced high entropy in non-oxide ceramic systems. 14,15 As the timeline Figure 1 shows, high entropy borides were discovered in 2016, 16 followed by high entropy nitrides, carbides, and sulfides in 2018, [17][18][19] high entropy fluorides, silicides and silicates in 2019, 7,9,20 high entropy layered hydroxides in 2020, 21 and high entropy MXene in 2022. 22 Among the high entropy ceramics, our present review focuses on the two Si-based high entropy ceramics, high entropy silicides and silicates.…”