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AVS2018 Session AC-ThP: Actinides and Rare Earths Poster Session

Thursday, October 25, 2018 6:00 PM in Room Hall B

Thursday Evening

Session Abstract Book
(265KB, May 6, 2020) Time Period ThP Sessions | Topic AC Sessions | Time Periods | Topics | AVS2018 Schedule

AC-ThP-1 Upconversion Photoluminescence Efficiency Dependence of Yb ions in Gd0.91-xNbO4: Ybx3+, Er0.09 SoungSoo Yi, Seung Gon Lee (Silla University, Republic of Korea) Gd_(0.91-x)NbO₄: Er³⁺_0.09, Yb³⁺_x(x= 0.03, 0.06, 0.09, 0.12 and 0.15) phosphors were synthesized by the facile solid state reaction method. Yb³⁺ concentrations were changed from 0.03 to 0.15 mol for the fixed Er³⁺concentration at 0.09 mol. The particle size of phosphors was around 180 ~ 350 nm and shape were angular oval observed by scanning electron microscopy. The crystalline structures of the phosphors were investigated by X-ray diffraction. The photoluminescence emission based on the green emissions near 528 and 551 nm and red emissions near 657 and 675 nm were observed and the highest emission intensity occurred for the sample Yb_0.15 Er_0.09. Also, under the 980 nm excitation, Er³⁺, Yb³⁺ co-doped GdNbO₄ phosphors appeared the up-conversion emission based on the green emission near 535 nm and 556 nm radiated by ²H_11/2→ ⁴I_15/2 and ⁴S_3/2→ ⁴I_15/2 transitions and red emission about 657 nm and 675 nm radiated by ⁴F_9/2→ ⁴I_15/2 transition, which assigned to the intra 4f transitions of Er³⁺ ions.
AC-ThP-2 Luminescence Characteristics of (Gd_0.85-xYb_0.15)NbO₄:Er_x³⁺ Phosphors SoungSoo Yi, DongGyu Lee (Silla University, Republic of Korea) Gd_(0.85-x)NbO₄: Yb³⁺_0.15, Er³⁺_x(x= 0.03, 0.06, 0.09, 0.12 and 0.15) phosphors were synthesized by the solid state reaction method. Er³⁺ concentrations were changed from 0.03 to 0.15 mol for the fixed Yb³⁺concentration at 0.15 mol. The crystalline structures of the phosphors were investigated by X-ray diffraction. The particle size of phosphors was around 140 ~ 320 nm and shape were angular oval observed by scanning electron microscopy. The photoluminescence emission based on the blue emission near 471 nm, green emission near 596 nm and red emission near 621 nm were observed and the highest emission intensity occurred for the sample Yb_0.15 Er_0.09. Also, under the 980 nm excitation, Er³⁺, Yb³⁺ co-doped GdNbO₄ phosphors appeared the up-conversion emission based on the green emission near 535 nm and 556 nm radiated by ²H_11/2→ ⁴I_15/2 and ⁴S_3/2→ ⁴I_15/2 transitions and red emission about 657 nm and 675 nm radiated by ⁴F_9/2→ ⁴I_15/2 transition, which assigned to the intra 4f transitions of Er³⁺ ions.
AC-ThP-3 Exploring the Electronic Structure of Molecular Lanthanide Complexes in the +2 Oxidation State Using Photoelectron Spectroscopy Daniel Huh, Jared Bruce, John Hemminger, William Evans (University of California, Irvine) Recent advances in rare-earth metal reduction chemistry have led to the isolation of a new series of Ln(II) complexes. For Ln = Y, La, Ce, Nd, Gd, Tb, Dy, Ho, Er, and Lu, reduction of 4fⁿ (C₅H₄SiMe₃)₃Ln^III complexes generates [(C₅H₄SiMe₃)₃Ln^II]^1– products that exhibit unusual 4fⁿ5d¹ mixed-principal quantum number electron configurations. X-ray photoelectron spectroscopy (XPS) has been employed to examine and compare these mixed-principal quantum number electronic structures with those of traditional Ln(II) complexes that have 4fⁿ⁺¹ configurations. In this work, X-ray and ultraviolet photoelectron spectroscopy have been used to examine the electronic structure of [K(2.2.2-cryptand)][(C₅H₄SiMe₃)₃Ln^II] (Ln = Eu, Gd, Tb) where Gd(II) and Tb(II) have previously been shown to have non-traditional 4f⁷5d¹ and 4f⁸5d¹ electronic configurations, respectively, and where Eu(II) has been shown to have a traditional 4f⁷ electronic configuration.
AC-ThP-4 Effects of Cerium Content on Local Structure in U1-xCexO2 Solid Solution Hanjie Cao (Shanghai Institute of Applied Physics, Chinese Academy of Science., China); Yuying Huang (Shanghai Institute of Applied Physics, Chinese Academy of Science, China) Uranium–cerium mixed oxides U_1-xCe_xO₂ (x=0.05, 0.20, 0.35, 0.50, 0.65, 0.80) were prepared by co-precipitation method. X-ray diffraction data shows that the U_1-xCe_xO₂ samples are solid solutions with lattice parameters following Vegard’s law . The local structures of U_1-xCe_xO₂ were studied by X-ray absorption fine structure spectroscopy at both U L₃ and Ce K edges. To avoid the interference from L₂ edge in Ce edge XAFS data, Ce K edge XAFS was used to obtain more accurate local structure of Ce. XAFS data shows that there is local structure disorder in U_1-xCe_xO₂ solid solution. The effects of Ce content on the local structure disorder in U_1-xCe_xO₂ solid solution were studied. For a cerium content less or equal to about 35%, the disorder increases with the addition of cerium in the U_1-xCe_xO₂ solid solution. When the cerium content increases to more than 50% the disorder of the sample decreases rapidly.
AC-ThP-5 Magnetism of the (Nd,R)₂Fe₁₄B - H system with R = Er and Tm Irina Tereshina, Lev Ivanov (M.V. Lomonosov Moscow State University, Russian Federation); Denis Gorbunov (Helmholtz-Zentrum Dresden-Rossendorf, Germany); Mykhaylo Paukov (Charles University, Prague, Czech Republic); Evgeniya Tereshina-Chitrova (Institute of Physics, Academy of Sciences of the Czech Republic); Mathias Doerr (Technische Universität Dresden, Germany); Ladislav Havela (Charles University, Prague, Czech Republic); Alexander V. Andreev (Institute of Physics ASCR, Czech Republic) Since the discovery in 1984, the R₂Fe₁₄B (R is a rare earth) compounds received a considerable scientific attention due to their hard magnetic properties [1,2]. Fundamental characteristics of the best permanent magnet Nd₂Fe₁₄B are known to be highly sensitive to the atomic substitutions and absorbed light atoms such as hydrogen. In the present work, we studied a combined influence of substitutions of Er and Tm for Nd and hydrogen absorption on the behavior of magnetization in magnetic fields up to 60 T. All studies were conducted on free powder samples at 2 K. It is found that the substitution in the rare earth sublattice decreases the saturation magnetization as a result of ferrimagnetic ordering of magnetic moments of heavy rare earths with respect to the moments of Nd and Fe. However, under sufficiently strong magnetic fields the magnetic moments rotate and in the ideal case, the field-induced ferromagnetic state is observed. This phenomenon is directly connected to the strength of the inter-sublattice exchange interactions (Fe and Nd, Er, Tm sublattices). In the parent materials (Nd_0.5Er_0.5)₂Fe₁₄B and (Nd_0.5Tm_0.5)₂Fe₁₄B in fields up to 60 T no increase of the magnetization was observed. Hydriding of the compounds up to the maximum possible hydrogen content 5.5 at.H/f.u. allows us to observe a forced-ferromagentic state in the (Nd_0.5Tm_0.5)₂Fe₁₄BH_5.5 compound. The transition from ferri- to the ferromagnetic state occurs gradually: it begins at the 35 T field and finishes at 55 T. For the compound (Nd_0.5Er_0.5)₂Fe₁₄BH_5.5 we also observe a magnetization increase. So that, hydrogenation is found to weaken the intersublattice exchange interaction in these three-sublattice materials. This work is performed with financial support of the grant of Russian Scientific Foundation (project № 18-13-00135). We acknowledge the support of HLD at HZDR (member of the European Magnetic Field Laboratory) and the Materials Growth and Measurement Laboratory (https://mgml.eu [https://mgml.eu/]). [1] J. F. Herbst, Rev. Mod. Phys . 63, 819 (1991). [2] O . Gutfleisch et . al . Advanced Mater . 23 (7), 821 (2011).

Session Abstract Book
(265KB, May 6, 2020) Time Period ThP Sessions | Topic AC Sessions | Time Periods | Topics | AVS2018 Schedule