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Results for “PRASEODYMIUM”

Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 19 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2015

Amphoteric doping of praseodymium Pr{sup 3+} in SrTiO{sub 3} grain boundaries

Charge compensation in rare-earth Praseodymium (Pr{sup 3+}) doped SrTiO{sub 3} plays an important role in determining the overall photoluminescence properties of the system. Here, the Pr{sup 3+} doping behavior in SrTiO{sub 3} grain boundaries (GBs) is analyzed using aberration corrected scanning transmission electron microscopy. The presence of Pr{sup 3+} induces structural variations and changes the statistical prevalence of the GB structures. In contrast to the assumption that Pr{sup 3+} substitutes on the Sr site in the bulk, Pr{sup 3+} is found to substitute on both Sr and Ti sites inside the GBs, with the highest concentration at the Ti sites. This amphoteric doping behavior in the boundary plane is further confirmed by first principles theoretical calculations.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2018

Volume collapse phase transitions in cerium-praseodymium alloys under high pressure

Cerium-12at%Praseodymium(Ce 0.88 Pr 0.12 ) and Ce-50at%Praseodymium(Ce 0.50 Pr 0.50 ) alloy samples that contain a random solid-solution of Ce (4f1 (J=5/2)) and Pr (4f2 (J=4)) localized f-states have been studied by angle dispersive x-ray diffraction in a diamond anvil cell to a pressure of 65 GPa and 150 GPa respectively using a synchrotron source. Ce 0.88 Pr 0.12 alloy crystallizes in a face-centered cubic (γ-phase) structure at ambient conditions, while Ce 0.50 Pr 0.50 alloy crystallizes in the double hexagonal close packed (dhcp) structure at ambient conditions. Two distinct volume collapse transitions are observed in Ce 0.88 Pr 0.12 alloy at 1.5 GPa and 18 GPa with volume change of 8.5% and 3% respectively. In contrast, Ce 0.50 Pr 0.50 alloy shows only a single volume collapse of 5.6% at 20 GPa on phase transformation to α-Uranium structure under high pressure. Electrical transport measurements under high pressure show anomalies in electrical resistance at phase transitions for both compositions of this alloy.

36 MATERIALS SCIENCE↗
DOE OSTI2013

Age hardening and creep resistance of cast Al–Cu alloy modified by praseodymium

The effects of praseodymium on age hardening behavior and creep resistance of cast Al–Cu alloy were investigated. The results indicated that praseodymium facilitated the formation of the θ′ precipitates during the age process and improved the hardness of the Al–Cu alloy. Besides, praseodymium resulted in the formation of the Al{sub 11}Pr{sub 3} phase in the grain boundaries and among the dendrites of the modified alloy. Because of the good thermal stability of Al{sub 11}Pr{sub 3} phase, it inhibits grain boundary migration and dislocation movement during the creep process, which contributes to the improvement in the creep resistance of the modified alloy at elevated temperatures. - Highlights: • Pr addition enhances the hardness and creep resistance of the Al–Cu alloy. • Pr addition facilitates the formation of the θ′ precipitates. • Pr addition results in the formation of the Al11Pr3 phase in the Al–Cu alloy.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Structural and magnetic properties of praseodymium substituted barium-based spinel ferrites

Highlights: • Barium based spinel ferrites were successfully synthesized by Sol-gel method. • The spinel phase has been observed in all samples. • Ac susceptibility of all the samples is presented. • The Ms Decreases with increasing Pr contents while Hc increases. - Abstract: In this research work BaPr{sub x}Fe{sub 2-x}O{sub 4} (x = 0.0, 0.025, 0.05, 0.075, 0.10) spinel ferrites have been synthesized successfully by sol-gel technique. X-ray diffraction analysis confirmed the fcc spinel phase of the synthesized samples. All the samples showed inhomogeneous grain size distribution observed through scanning electron microscopy (SEM).Temperature dependence normalized AC susceptibility and Curie temperature studies revealed that BaFe{sub 2}O{sub 4} exhibited multidomain (MD) structure with high Curie temperature. On the other hand, multidomain to single domain (SD) transitions occurred when the praseodymium is substituted into barium spinel ferrites. Narrow loops showed the soft nature of ferrites and it was confirmed from magnetic properties of the prepared samples. Decreasing trend of saturation magnetization and remanence was observed with the substitution of praseodymium contents. Coercivity and anisotropy constant both enhanced with the praseodymium concentration. The above-mentioned parameters revealed that the synthesized spinel ferrites might be useful for the of high-density magnetic recording applications.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2022

Studies toward the Use of Ionic Liquids and Supercritical CO 2 for the Recovery and Separation of Praseodymium from Waste Streams

Waste streams from the incineration of metal-containing materials like such as computer processor boards and batteries may contain critical rare earth elements like praseodymium. Data on the solubility of Pr compounds and on their distribution coefficients in supercritical CO 2 /ionic liquid two-phase systems are important to determine if an ionic liquid/supercritical CO 2 two-phase approach is feasible toward the recovery of a particular metal. This work provides data on the solubility of various praseodymium compounds in butyl-methyl-pyrrolidinium bis(trifluoromethylsulfonyl)imide (BMPyTf2N) ionic liquid and on the distribution coefficients of these praseodymium compounds in the supercritical CO 2 phase of the two-phase BMPyTf2N ionic liquid/supercritical CO 2 system, with and without a tributyl phosphate additive.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2025

Praseodymium in the formal +5 oxidation state

Praseodymium in the +5 oxidation state is a long-sought connection between lanthanide, early-transition and actinide metal redox chemistries. Unique among the lanthanide series, evidence for molecular pentavalent praseodymium species has been observed in the gas phase and noble gas matrix isolation conditions. Here we report the low-temperature synthesis and characterization of a molecular praseodymium complex in the formal +5 oxidation state, [Pr 5+ (NP t Bu 3 ) 4 ][X − ] (where t Bu = tert -butyl and X − = tetrakis(pentafluorophenyl)borate or hexafluorophosphate). Single-crystal X-ray diffraction, solution-state spectroscopic, solution magnetometric, density functional theory and multireference wavefunction-based methods indicate a highly multiconfigurational singlet ground state. Finally, an inverted ligand field drives this unique electronic structure, which establishes a critical link in understanding the bonding of high-valent metal complexes across the periodic table.

chemical bonding↗
DOE OSTI2016

Optical characterization of ZnO nanomaterial with praseodymium ions

ZnO nanomaterial with praseodymium ions was prepared by chemical synthesis method. The ZnO nanomaterial was characterized by XRD, SEM and TEM. Their absorption in UV-VIS/NIR regions was measured at room temperature. The experimental oscillator strengths were calculated from the areas under the absorption bands. Eight absorption bands have been observed. From these spectral data various energy interaction parameters like Slater–Condon, Lande, Racah, Nephelauxetic ratio and bonding parameters have been computed. Judd-Ofelt analysis has been carried out using the absorption spectra to evaluate the radiative properties for luminescent levels of the praseodymium ion and discussed. The observed nano particle size is 2nm.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Thermodynamic characteristics of praseodymium in the gallium–aluminum eutectic melt

The Ga–Al eutectic melt saturated with praseodymium was studied in the temperature range 572–1076 K by electromotive force (emf) method relative to the reference electrode (In{sub L} + PrIn{sub 3}, where L is the liquid phase) in a LiCl–KCl–CsCl eutectic electrolyte. The partial molar thermodynamic functions (enthalpy, entropy, and Gibbs energy) of praseo dymium in a Ga–Al eutectic melt were calculated. According to the emf measurements of the two-phase Pr–Ga–Al{sub L} + intermetallic compound alloys equilibrated with the Ga–Al eutectic melt saturated with praseodymium, there are intermetallic compounds PrGa{sub 6}, PrGa{sub 4}, and Pr{sub 0.22}Ga{sub 0.78}(PrGa{sub 2}) in the temperature ranges 572–741, 741–883, and 883–1076 K, respectively.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2022

Pr(H 3 BNMe 2 BH 3 ) 3 and Pr(thd) 3 as Volatile Carriers for Actinium-225. Deposition of Actinium-Doped Praseodymium Boride Thin Films for Potential Use in Brachytherapy

Here we show that the praseodymium N,N-dimethylaminodiboranate complex Pr(H 3 BNMe 2 BH 3 ) 3 and the 2,2,6,6-tetramethylheptane-3,5-dionate complex Pr(thd) 3 can serve as volatile carriers for 225 Ac. The actinium coordination complexes Ac(H 3 BNMe 2 BH 3 ) 3 and Ac(thd) 3 are the likely species subliming with the carrier material. A sample of 225 Ac-doped Pr(H 3 BNMe 2 BH 3 ) 3 was used to deposit amorphous 225 Ac-doped praseodymium boride films on glass and Si(100) at 300 °C. Furthermore, the α emission spectra of the refractory films are well-resolved, suggesting that they could be used as radioactive implants for brachytherapy and related treatments.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2019

Investigative Studies toward the Extraction and Recovery of Praseodymium From Ionic Liquids Using Supercritical Carbon Dioxide

Recycle of rare earth elements requires the extraction and recovery of these metals from consumer products such as rechargeable batteries, electric motor magnets, and aircraft engines once the rare earths have been oxidatively dissolved. One approach to this is to combine the metal extraction and recovery steps into a continuous process. Such a scheme would involve direct-dissolution and ligand-assisted supercritical fluid extraction of the metal, followed by deposition of the extracted metal complex into an ionic liquid where it can be electrochemically reduced to its metallic state. Whereas supercritical fluid extraction of rare earth metals has been recently studied, deposition of rare earth metal-ligand complexes into an ionic liquid is not well known for many rare earth metal-ligand systems. In these studies we measured the solubility of several Praseodymium complexes in scCO2. We also measured the solubility of the Praseodymium complexes in ionic liquids with different physical properties of interest including polarizability, viscosity, and conductivity. The ionic liquids studied are from the pyrrolidinium family and include n-butyl-n-methylpyrrolidinium bis(trifluoromethylsulfonyl) imide (BMPy TFSI). Upon completion of these experiments, we added an additional modifier to the ionic liquid solution in the form of a chelating agent and carbon dioxide. Overall, the additions of the various chelating agents and BMPy TFSI result in large changes to viscosity, conductivity, and metal complexation properties of the solutions. Here we report the results of our findings and discuss the possibility of tuning the extractive and reductive properties of the solutions by picking ionic liquids and chelating agents with physical properties conducive to the desired metal recovery scheme.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2014

Electronic and optical properties of Praseodymium trifluoride

We report the role of f- states on electronic and optical properties of Praseodymium trifluoride (PrF{sub 3}) compound. Full potential linearized augmented plane wave (FPLAPW) method with the inclusion of spin orbit coupling has been used. We employed the local spin density approximation (LSDA) and Coulomb-corrected local spin density approximation (LSDA+U). LSDA+U is known for treating the highly correlated 4f electrons properly. Our theoretical investigation shows that LSDA+U approximation reproduce the correct insulating ground state of PrF{sub 3}. On the other hand there is no significant difference of reflectivity calculated by LSDA and LSDA+U. We find that the reflectivity for PrF{sub 3} compound stays low till around 7 eV which is consistent with their large energy gaps. Our calculated reflectivity compares well with the experimental data. The results are analyzed in the light of transitions involved.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2019

Effect of the J–J Interaction of Excited States of the Rare-Earth Ion Pr{sup 3+} on Magnetically Polarized Luminescence of Praseodymium-Yttrium Aluminum Garnet

The spectra of luminescence and magnetic circular polarization of luminescence of praseodymium–yttrium aluminum garnet Pr{sup 3+} : Y{sub 3}Al{sub 5}O{sub 12} (PrYAG) are studied in the visible spectral region at temperature T = 300 K. An analysis of spectral dependences of magnetooptical and optical spectra makes it possible to identify optical 4 f–4 f-transitions between Stark sublevels of multiplets {sup 3}P{sub 0}, {sup 3}P{sub 1}, {sup 3}Н{sub 5}, and {sup 3}Н{sub 6} in PrYAG. It was shown that an important role in the spectrum of the degree of magnetic circular polarization of luminescence of this paramagnetic garnet is played by the effect of quantum-mechanical J–J mixing of states of Stark singlets {sup 3}Н{sub 5} and {sup 3}Н{sub 6} of non-Kramer rare-earth ion Pr{sup 3+} in the “green” luminescence band related to forbidden 4 f → 4 f transition {sup 3}P{sub 0} → {sup 3}Н{sub 5} in the visible spectral region. To interpret the spectra of magnetic circular polarization of luminescence, the energy of experimentally determined Stark sublevels of multiplets under study, their irreducible representations and wave functions determined by numerical simulation of the energy spectrum of the rare-earth ion Pr{sup 3+} in the garnet structure are used.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2017

Magnetic interactions in praseodymium ruthenate Pr{sub 3}RuO{sub 7} with fluorite-related structure

Solid solutions Pr{sub 3}(Ru{sub 1-x}Ta{sub x})O{sub 7} (0≤x≤1.0) and (Pr{sub 1-x}Y{sub x}){sub 3}RuO{sub 7} (0≤x≤0.7) were obtained as a single phase compound. They crystallize in an orthorhombic superstructure derived from that of the cubic fluorite with space group Cmcm. The results of the Rietveld analysis for X-ray diffraction profiles of Pr{sub 3}(Ru{sub 1-x}Ta{sub x})O{sub 7} showed that Ru and Ta atoms are randomly situated at the six-coordinate 4b site. For (Pr{sub 1-x}Y{sub x}){sub 3}RuO{sub 7}, with increasing the concentration of Y ions (x value), the smaller Y ions occupy selectively the seven-coordinate 8g site rather than the eight-coordinate 4a site. Through magnetic susceptibility measurements for Pr{sub 3}(Ru{sub 1-x}Ta{sub x})O{sub 7}, the antiferromagnetic transition temperatures decrease linearly with increasing x value, and at x=0.75 no magnetic ordering was found down to 1.8 K, indicating the magnetic interaction is not one-dimensional, but three-dimensional. On the other hand, the antiferromagnetic transition temperature for (Pr{sub 1-x}Y{sub x}){sub 3}RuO{sub 7} decreases with increasing x value, but above x≥0.50 it becomes constant (~12 K). This result indicates that Pr{sup 3+} ions at the seven-coordinate site greatly contribute to the antiferromagnetic interactions observed in (Pr{sub 1-x}Y{sub x}){sub 3}RuO{sub 7}. Density functional calculations of Pr{sub 3}RuO{sub 7} demonstrate that the electronic structure gives insulating character and that oxygen 2p orbitals hybridize strongly with Ru 4d orbitals in the valence band (VB). Near the top of VB, the Pr 4 f orbitals at the seven-coordinated site also show a weak hybridization with the O(1) 2p orbitals. The Ru-O(1)-Pr superexchange pathway take part in three-dimensional magnetic interaction and play an important role in an enhancement of long-range magnetic ordering. - Graphical abstract: The spin densities and the spin polarization of Pr{sub 3}RuO{sub 7} are shown. Significant spin polarization is seen on the magnetic Pr and Ru ions, but there is also some on the O(1), (3) ligands of Ru. - Highlights: • New fluorite-related quaternary praseodymium ruthenates were prepared. • Pr{sub 3}RuO{sub 7} shows an antiferromagnetic transition at 55 K. • The Ru-O-Pr superexchange interactions are three-dimensional.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2013

Synthesis and structural studies of praseodymium doped silver borate glasses

Praseodymium doped silver borate glasses with nominal composition xPr{sub 6}O{sub 11}-(25-x)Ag{sub 2}O-75B{sub 2}O{sub 3} (x=0, 1, 2, 3, 4, 5) were prepared by melt quench technique. XRD pattern shows that there is no sharp peak it confirms the amorphous nature of the present glasses. The glass transition temperature (T{sub g}) of this glass system have been studied using the Matac MBS-8000 Digital Signal Processing and Conventional Thermal Analysis (DTA) method. The T{sub g} of these glasses increases with increase in concentration of Pr{sub 6}O{sub 11} except at 0.2 mol%, T{sub g} value is lower. {sup 11}B MAS-NMR shows the presence of sharp peak around 0.306 ppm. Chemical shift of these glasses decreases with mol% of rare earth oxide. FTIR spectra recorded in the region of 400 to 4000 cm{sup -1}. This studies revealed that the progressive addition Ag{sub 2}O and Pr{sub 6}O{sub 11} leads to modification of B{sub 2}O{sub 3} into BO{sub 4} groups. Raman measurements of these glasses support the proposed interpretations of the experimental results.

36 MATERIALS SCIENCE↗