Journal of Rare Earths最新文献

A novel microstructure of magnetically anisotropic SmCo-based magnet with high-performance is reported. The magnet consists of SmCo₇-H (TbCu₇-hexagonal type), Sm₂Co₁₇–H (Th₂Ni₁₇-hexagonal type) and SmCo₃-R (SmCo₃-rhombohedral type) phases. The maximum magnetic energy product of the magnet is 231.69 kJ/m³, and the intrinsic coercivity is 1005.47 kA/m. An outstanding intrinsic coercivity temperature coefficient (β) of −0.125%/K between 298 and 773 K is obtained, which is very close to the β of commercial high-temperature Sm₂Co₁₇-based sintered magnets. The initial magnetization curve indicates that the coercivity mechanism is controlled by a domain wall pinning mechanism. The SmCo₃-R lamellar phase may be a potential pinning center or self-pinning center. The microstructure of the magnet is different from that of any previous SmCo-based magnets. These findings provide a new idea for preparing high-performance SmCo-based permanent magnets.

Highly pure red phosphors LiM(PO₃)₃:Eu³⁺ (M = Sr, Ca) doped with Eu³⁺ (1 mol%) were synthesized via solution combustion method and their crystal structure and luminescence dynamics were studied to explore its suitability in white light emitting diodes. The Rietveld refinement analysis of the powder X-ray diffraction patterns reveals that the phosphors belong to the pure triclinic phase of LiSr(PO₃)₃ and LiCa(PO₃) with space group P-$\overline{1}$ (2). The scanning electron microscopy images showed the agglomerated morphology. The photoluminescence emission spectra under 393 nm show an orange band at 594 nm and a red band at 613 nm ascribed to ⁵D₀ → ⁷F₁, ⁵D₀ → ⁷F₂ transitions of Eu³⁺ ion in both the phosphors. Moreover, the spectroscopic properties such as luminescence behaviour, and Stark splitting were used to examine the symmetry of Eu³⁺ ions in LiM(PO₃)₃:Eu³⁺ (M = Sr, Ca) phosphors in terms of distortion induced upon doping. The Stark splitting shows that the actual site symmetry for Eu³⁺ ion was estimated to be D₂ type for both phosphors. The photometric properties of LiCa(PO₃)₃:Eu³⁺ such as Commission International de l’Eclairage coordinates (x = 0.64, y = 0.36) near to the standard one (red), high color purity (95%) and higher brightness reveal that the phosphor has the capability of acting as a red component in n-UV white light emitting diodes.

Bastnaesite ((Ce,La,Pr,Nd)CO₃F) is a significant light rare earth mineral found in nature, known for its fine-grained properties. Flotation is commonly employed for the recovery of fine-grained bastnaesite particles. Collectors serve as an essential flotation reagent that enhance the surface hydrophobicity of target minerals. A novel collector, N-hydroxy-9-octadecenamide (N-OH-9-ODA), was synthesised in this study. N-OH-9-ODA exhibits superior selectivity compared to the traditional collector oleic acid in the flotation separation of bastnaesite and fluorite. The experimental and computational results indicate that N-OH-9-ODA exhibits superior selectivity due to its higher adsorption affinity for bastnaesite surface compared to fluorite surface. The zeta potential and the binding energies of the Ce 3d peaks in the X-ray photoelectron spectrum (XPS) of bastnaesite surface exhibit significant shifts. Conversely, fluorite surface demonstrates minimal alterations in its zeta potential and the binding energies of the Ca 2p peaks in its XPS after its interaction with N-OH-9-ODA.

CeCO₃OH has a unique crystal structure and excellent optical, electronic and catalytic properties, which has been widely investigated for many applications. Interestingly, ceria obtained from CeCO₃OH has a morphology that is similar to that of the precursor, and the CeO₂-based products obtained from CeCO₃OH exhibit outstanding properties, such as catalytic performances, owing to their designed morphology and oxygen vacancies (OVs). To introduce CeCO₃OH into a wider range of potential researchers, we first systematically review the physico-chemical properties, synthesis, reaction and morphology tuning mechanism of CeCO₃OH, and summarize the conversion behavior from CeCO₃OH to ceria. Then, we thoroughly survey the applications of CeCO₃OH and its conversion products. Suggestions for further investigations of CeCO₃OH are also made in this review. It is hoped that the exhaustive compilation of the valuable properties and considerable potential investigations of CeCO₃OH will promote further applications of CeCO₃OH and CeO₂-based functional materials.

Dual-excitation and dual-emission Y₄GeO₈:Bi³⁺,Sm³⁺ phosphors were manufactured by traditional solid-phase sintering technique. The X-ray diffraction, morphology, photoluminescence, energy transfer process and temperature sensing properties of Y₄GeO₈:Bi³⁺,Sm³⁺ samples were comprehensively evaluated. The Y₄GeO₈:Bi³⁺,Sm³⁺ phosphors exhibit characteristic emissions of Bi³⁺ (³P₁→¹S₀) and Sm³⁺ (⁴G_5/2→⁶H) under both 290 and 347 nm excitations. In fluorescence intensity ratio and Commission International de L'Eclairage coordinates modes, Y₄GeO₈:Bi³⁺,Sm³⁺ samples present excellent temperature measurement performance. The maximum relative sensitivity (S_r-max) values of the former are 1.55%/K (460 K, 290 nm excitation) and 0.82%/K (506 K, 347 nm excitation). The S_r-max(x) values of the latter are 0.21%/K (437 K, 290 nm excitation) and 0.15%/K (513 K, 347 nm excitation). These results illustrate that Y₄GeO₈:Bi³⁺,Sm³⁺ phosphors can be used as a candidate material for a dual-mode optical thermometer under dual-excitation.

In current report, the structural, magnetic, and thermoelectric properties of RE doped MgPm₂X₄ (X = S, Se) spinels were investigated. The energy difference in ferromagnetic and antiferromagnetic states reveals the stability of MgPm₂(S/Se)₄ in the ferromagnetic states. The computation of enthalpy of formation also ascertains thermodynamic stability of crystal structure. Spin-dependent band structure and density of states analysis reveal ferromagnetic semiconducting character showing different electronic behavior in both spin channels. The room temperature ferromagnetism, spin polarization and Curie temperature are estimated from exchange energies analysis. In addition, exchange constants (N₀α and N₀β), exchange energy Δ_x(pd), crystal field energy, and double exchange mechanism were studied to explore the magnetic response. Likewise, the electrical conductivity, thermal conductivity, Seebeck co-efficient, and power factor show effect on electrons spin and their potential for thermoelectric devices.