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At least 163 records · Page 9
All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Materials Data on Pr(BRu)4 by Materials Project

Pr(RuB)4 crystallizes in the tetragonal I4_1/acd space group. The structure is three-dimensional. Pr3+ is bonded to twelve equivalent B3- atoms to form distorted PrB12 cuboctahedra that share corners with twelve equivalent RuB5 trigonal bipyramids, edges with twelve equivalent PrB12 cuboctahedra, edges with four equivalent RuB5 trigonal bipyramids, and faces with twelve equivalent RuB5 trigonal bipyramids. There are a spread of Pr–B bond distances ranging from 3.01–3.23 Å. Ru+2.25+ is bonded to five equivalent B3- atoms to form distorted RuB5 trigonal bipyramids that share corners with three equivalent PrB12 cuboctahedra, corners with eight equivalent RuB5 trigonal bipyramids, an edgeedge with one PrB12 cuboctahedra, edges with six equivalent RuB5 trigonal bipyramids, and faces with three equivalent PrB12 cuboctahedra. There are a spread of Ru–B bond distances ranging from 2.16–2.32 Å. B3- is bonded in a 6-coordinate geometry to three equivalent Pr3+, five equivalent Ru+2.25+, and one B3- atom. The B–B bond length is 1.81 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Pr(CuO2)2 by Materials Project

Pr(CuO2)2 crystallizes in the monoclinic C2/c space group. The structure is three-dimensional. Pr4+ is bonded in a 8-coordinate geometry to eight O2- atoms. There are four shorter (2.50 Å) and four longer (2.51 Å) Pr–O bond lengths. There are two inequivalent Cu2+ sites. In the first Cu2+ site, Cu2+ is bonded in a square co-planar geometry to four O2- atoms. There is two shorter (1.91 Å) and two longer (1.92 Å) Cu–O bond length. In the second Cu2+ site, Cu2+ is bonded in a square co-planar geometry to four O2- atoms. There is two shorter (1.91 Å) and two longer (1.92 Å) Cu–O bond length. There are two inequivalent O2- sites. In the first O2- site, O2- is bonded to two equivalent Pr4+ and two Cu2+ atoms to form a mixture of distorted edge and corner-sharing OPr2Cu2 tetrahedra. In the second O2- site, O2- is bonded to two equivalent Pr4+ and two Cu2+ atoms to form a mixture of distorted edge and corner-sharing OPr2Cu2 tetrahedra.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Pr(HoS2)3 by Materials Project

Pr(HoS2)3 crystallizes in the monoclinic P2_1/m space group. The structure is three-dimensional. there are three inequivalent Ho3+ sites. In the first Ho3+ site, Ho3+ is bonded to seven S2- atoms to form distorted HoS7 pentagonal bipyramids that share corners with three HoS6 octahedra, edges with two equivalent HoS6 octahedra, and edges with four equivalent HoS7 pentagonal bipyramids. The corner-sharing octahedra tilt angles range from 38–51°. There are a spread of Ho–S bond distances ranging from 2.69–2.92 Å. In the second Ho3+ site, Ho3+ is bonded to six S2- atoms to form HoS6 octahedra that share corners with three equivalent HoS6 octahedra, a cornercorner with one HoS7 pentagonal bipyramid, edges with four equivalent HoS6 octahedra, and edges with two equivalent HoS7 pentagonal bipyramids. The corner-sharing octahedra tilt angles range from 55–61°. There are a spread of Ho–S bond distances ranging from 2.67–2.77 Å. In the third Ho3+ site, Ho3+ is bonded to six S2- atoms to form HoS6 octahedra that share corners with three equivalent HoS6 octahedra, corners with two equivalent HoS7 pentagonal bipyramids, and edges with four equivalent HoS6 octahedra. The corner-sharing octahedra tilt angles range from 55–61°. There are a spread of Ho–S bond distances ranging from 2.65–2.79 Å. Pr3+ is bonded in a 8-coordinate geometry to eight S2- atoms. There are a spread of Pr–S bond distances ranging from 2.91–3.05 Å. There are six inequivalent S2- sites. In the first S2- site, S2- is bonded in a 4-coordinate geometry to four Ho3+ atoms. In the second S2- site, S2- is bonded to three Ho3+ and one Pr3+ atom to form distorted SPrHo3 trigonal pyramids that share corners with two equivalent SPr2Ho3 square pyramids, corners with four SPr2Ho3 trigonal bipyramids, corners with two equivalent SPrHo3 trigonal pyramids, edges with three equivalent SPr2Ho3 square pyramids, and edges with two equivalent SPr3Ho2 trigonal bipyramids. In the third S2- site, S2- is bonded in a rectangular see-saw-like geometry to four Ho3+ atoms. In the fourth S2- site, S2- is bonded to three equivalent Ho3+ and two equivalent Pr3+ atoms to form distorted SPr2Ho3 square pyramids that share corners with six SPr2Ho3 trigonal bipyramids, corners with two equivalent SPrHo3 trigonal pyramids, edges with four equivalent SPr2Ho3 square pyramids, edges with two SPr2Ho3 trigonal bipyramids, and edges with three equivalent SPrHo3 trigonal pyramids. In the fifth S2- site, S2- is bonded to three Ho3+ and two equivalent Pr3+ atoms to form distorted SPr2Ho3 trigonal bipyramids that share corners with two equivalent SPr2Ho3 square pyramids, corners with two equivalent SPr3Ho2 trigonal bipyramids, corners with three equivalent SPrHo3 trigonal pyramids, an edgeedge with one SPr2Ho3 square pyramid, and edges with five SPr2Ho3 trigonal bipyramids. In the sixth S2- site, S2- is bonded to two equivalent Ho3+ and three equivalent Pr3+ atoms to form distorted SPr3Ho2 trigonal bipyramids that share corners with four equivalent SPr2Ho3 square pyramids, corners with two equivalent SPr2Ho3 trigonal bipyramids, a cornercorner with one SPrHo3 trigonal pyramid, an edgeedge with one SPr2Ho3 square pyramid, edges with seven SPr2Ho3 trigonal bipyramids, and edges with two equivalent SPrHo3 trigonal pyramids.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Pr(Mo3Se4)2 by Materials Project

Pr(Mo3Se4)2 crystallizes in the trigonal R-3 space group. The structure is three-dimensional. Pr3+ is bonded in a body-centered cubic geometry to eight Se2- atoms. There are two shorter (2.91 Å) and six longer (3.18 Å) Pr–Se bond lengths. Mo+2.17+ is bonded to five Se2- atoms to form a mixture of edge and corner-sharing MoSe5 square pyramids. There are a spread of Mo–Se bond distances ranging from 2.53–2.77 Å. There are two inequivalent Se2- sites. In the first Se2- site, Se2- is bonded in a 1-coordinate geometry to one Pr3+ and three equivalent Mo+2.17+ atoms. In the second Se2- site, Se2- is bonded in a 5-coordinate geometry to one Pr3+ and four equivalent Mo+2.17+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Pr(Ni2B)6 by Materials Project

Pr(Ni2B)6 crystallizes in the orthorhombic Cmc2_1 space group. The structure is three-dimensional. Pr3+ is bonded in a distorted hexagonal planar geometry to six B3- atoms. There are a spread of Pr–B bond distances ranging from 3.04–3.31 Å. There are seven inequivalent Ni+1.25+ sites. In the first Ni+1.25+ site, Ni+1.25+ is bonded in a distorted T-shaped geometry to three B3- atoms. There are two shorter (2.10 Å) and one longer (2.19 Å) Ni–B bond lengths. In the second Ni+1.25+ site, Ni+1.25+ is bonded in a T-shaped geometry to three B3- atoms. There are two shorter (2.00 Å) and one longer (2.07 Å) Ni–B bond lengths. In the third Ni+1.25+ site, Ni+1.25+ is bonded to four B3- atoms to form a mixture of corner and edge-sharing NiB4 tetrahedra. There are a spread of Ni–B bond distances ranging from 2.00–2.10 Å. In the fourth Ni+1.25+ site, Ni+1.25+ is bonded in a distorted T-shaped geometry to three B3- atoms. There are a spread of Ni–B bond distances ranging from 2.03–2.11 Å. In the fifth Ni+1.25+ site, Ni+1.25+ is bonded to four B3- atoms to form a mixture of distorted corner and edge-sharing NiB4 tetrahedra. There are a spread of Ni–B bond distances ranging from 2.02–2.11 Å. In the sixth Ni+1.25+ site, Ni+1.25+ is bonded to four B3- atoms to form a mixture of distorted corner and edge-sharing NiB4 tetrahedra. There are a spread of Ni–B bond distances ranging from 2.03–2.12 Å. In the seventh Ni+1.25+ site, Ni+1.25+ is bonded in a distorted T-shaped geometry to three B3- atoms. There are a spread of Ni–B bond distances ranging from 2.06–2.13 Å. There are four inequivalent B3- sites. In the first B3- site, B3- is bonded in a 7-coordinate geometry to one Pr3+ and seven Ni+1.25+ atoms. In the second B3- site, B3- is bonded in a 7-coordinate geometry to one Pr3+ and seven Ni+1.25+ atoms. In the third B3- site, B3- is bonded in a 7-coordinate geometry to one Pr3+ and seven Ni+1.25+ atoms. In the fourth B3- site, B3- is bonded in a 7-coordinate geometry to one Pr3+ and seven Ni+1.25+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Pr(ErS2)3 by Materials Project

Pr(ErS2)3 crystallizes in the monoclinic P2_1/m space group. The structure is three-dimensional. there are three inequivalent Er3+ sites. In the first Er3+ site, Er3+ is bonded to seven S2- atoms to form distorted ErS7 pentagonal bipyramids that share corners with three ErS6 octahedra, edges with two equivalent ErS6 octahedra, and edges with four equivalent ErS7 pentagonal bipyramids. The corner-sharing octahedra tilt angles range from 39–51°. There are a spread of Er–S bond distances ranging from 2.68–2.91 Å. In the second Er3+ site, Er3+ is bonded to six S2- atoms to form ErS6 octahedra that share corners with three equivalent ErS6 octahedra, a cornercorner with one ErS7 pentagonal bipyramid, edges with four equivalent ErS6 octahedra, and edges with two equivalent ErS7 pentagonal bipyramids. The corner-sharing octahedra tilt angles range from 56–61°. There are a spread of Er–S bond distances ranging from 2.66–2.77 Å. In the third Er3+ site, Er3+ is bonded to six S2- atoms to form ErS6 octahedra that share corners with three equivalent ErS6 octahedra, corners with two equivalent ErS7 pentagonal bipyramids, and edges with four equivalent ErS6 octahedra. The corner-sharing octahedra tilt angles range from 56–61°. There are a spread of Er–S bond distances ranging from 2.65–2.78 Å. Pr3+ is bonded in a 8-coordinate geometry to eight S2- atoms. There are a spread of Pr–S bond distances ranging from 2.92–3.05 Å. There are six inequivalent S2- sites. In the first S2- site, S2- is bonded in a 4-coordinate geometry to four Er3+ atoms. In the second S2- site, S2- is bonded to three Er3+ and one Pr3+ atom to form distorted SPrEr3 trigonal pyramids that share corners with two equivalent SPr2Er3 square pyramids, corners with four SPr2Er3 trigonal bipyramids, corners with two equivalent SPrEr3 trigonal pyramids, edges with three equivalent SPr2Er3 square pyramids, and edges with two equivalent SPr3Er2 trigonal bipyramids. In the third S2- site, S2- is bonded in a distorted rectangular see-saw-like geometry to four Er3+ atoms. In the fourth S2- site, S2- is bonded to three equivalent Er3+ and two equivalent Pr3+ atoms to form distorted SPr2Er3 square pyramids that share corners with six SPr2Er3 trigonal bipyramids, corners with two equivalent SPrEr3 trigonal pyramids, edges with four equivalent SPr2Er3 square pyramids, edges with two SPr2Er3 trigonal bipyramids, and edges with three equivalent SPrEr3 trigonal pyramids. In the fifth S2- site, S2- is bonded to three Er3+ and two equivalent Pr3+ atoms to form distorted SPr2Er3 trigonal bipyramids that share corners with two equivalent SPr2Er3 square pyramids, corners with two equivalent SPr3Er2 trigonal bipyramids, corners with three equivalent SPrEr3 trigonal pyramids, an edgeedge with one SPr2Er3 square pyramid, and edges with five SPr2Er3 trigonal bipyramids. In the sixth S2- site, S2- is bonded to two equivalent Er3+ and three equivalent Pr3+ atoms to form distorted SPr3Er2 trigonal bipyramids that share corners with four equivalent SPr2Er3 square pyramids, corners with two equivalent SPr2Er3 trigonal bipyramids, a cornercorner with one SPrEr3 trigonal pyramid, an edgeedge with one SPr2Er3 square pyramid, edges with seven SPr2Er3 trigonal bipyramids, and edges with two equivalent SPrEr3 trigonal pyramids.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Pr(YS2)3 by Materials Project

Pr(YS2)3 crystallizes in the monoclinic P2_1/m space group. The structure is three-dimensional. Pr3+ is bonded in a 8-coordinate geometry to eight S2- atoms. There are a spread of Pr–S bond distances ranging from 2.92–3.06 Å. There are three inequivalent Y3+ sites. In the first Y3+ site, Y3+ is bonded to seven S2- atoms to form distorted YS7 pentagonal bipyramids that share corners with three YS6 octahedra, edges with two equivalent YS6 octahedra, and edges with four equivalent YS7 pentagonal bipyramids. The corner-sharing octahedra tilt angles range from 38–51°. There are a spread of Y–S bond distances ranging from 2.71–2.95 Å. In the second Y3+ site, Y3+ is bonded to six S2- atoms to form YS6 octahedra that share corners with three equivalent YS6 octahedra, a cornercorner with one YS7 pentagonal bipyramid, edges with four equivalent YS6 octahedra, and edges with two equivalent YS7 pentagonal bipyramids. The corner-sharing octahedra tilt angles range from 55–61°. There are a spread of Y–S bond distances ranging from 2.68–2.78 Å. In the third Y3+ site, Y3+ is bonded to six S2- atoms to form YS6 octahedra that share corners with three equivalent YS6 octahedra, corners with two equivalent YS7 pentagonal bipyramids, and edges with four equivalent YS6 octahedra. The corner-sharing octahedra tilt angles range from 55–61°. There are a spread of Y–S bond distances ranging from 2.67–2.81 Å. There are six inequivalent S2- sites. In the first S2- site, S2- is bonded in a 4-coordinate geometry to four Y3+ atoms. In the second S2- site, S2- is bonded to one Pr3+ and three Y3+ atoms to form distorted SPrY3 trigonal pyramids that share corners with two equivalent SPr2Y3 square pyramids, corners with four SPr2Y3 trigonal bipyramids, corners with two equivalent SPrY3 trigonal pyramids, edges with three equivalent SPr2Y3 square pyramids, and edges with two equivalent SPr3Y2 trigonal bipyramids. In the third S2- site, S2- is bonded in a rectangular see-saw-like geometry to four Y3+ atoms. In the fourth S2- site, S2- is bonded to two equivalent Pr3+ and three equivalent Y3+ atoms to form distorted SPr2Y3 square pyramids that share corners with six SPr2Y3 trigonal bipyramids, corners with two equivalent SPrY3 trigonal pyramids, edges with four equivalent SPr2Y3 square pyramids, edges with two SPr2Y3 trigonal bipyramids, and edges with three equivalent SPrY3 trigonal pyramids. In the fifth S2- site, S2- is bonded to two equivalent Pr3+ and three Y3+ atoms to form distorted SPr2Y3 trigonal bipyramids that share corners with two equivalent SPr2Y3 square pyramids, corners with two equivalent SPr3Y2 trigonal bipyramids, corners with three equivalent SPrY3 trigonal pyramids, an edgeedge with one SPr2Y3 square pyramid, and edges with five SPr2Y3 trigonal bipyramids. In the sixth S2- site, S2- is bonded to three equivalent Pr3+ and two equivalent Y3+ atoms to form distorted SPr3Y2 trigonal bipyramids that share corners with four equivalent SPr2Y3 square pyramids, corners with two equivalent SPr2Y3 trigonal bipyramids, a cornercorner with one SPrY3 trigonal pyramid, an edgeedge with one SPr2Y3 square pyramid, edges with seven SPr2Y3 trigonal bipyramids, and edges with two equivalent SPrY3 trigonal pyramids.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Structure and thermodynamics of calcium rare earth silicate oxyapatites, Ca 2 RE 8 (SiO 4 ) 6 O 2 (RE = Pr, Tb, Ho, Tm)

Calcium rare earth silicate oxyapatites, (Ca 2 RE 8 (SiO 4 ) 6 O 2 ), are of interest as components of glass-ceramic nuclear waste forms. To assess their long-term behavior in a geologic repository, it is essential to determine their structure and thermodynamic stability at relevant conditions. Here, in this work, we performed detailed structural and thermodynamic investigations on Ca 2 Pr 8 (SiO 4 ) 6 O 2 , Ca 2 Tb 8 (SiO 4 ) 6 O 2 , Ca 2 Ho 8 (SiO 4 ) 6 O 2 , and Ca 2 Tm 8 (SiO 4 ) 6 O 2 by high energy synchrotron powder X-ray diffraction combined with Rietveld analysis and high temperature oxide melt drop solution calorimetry. Enthalpies of formation from constituent oxides (ΔH f,ox ) were determined to be -765.1 ± 22.8 kJ/mol for Ca 2 Pr 8 (SiO 4 ) 6 O 2 ; -638.9 ± 20.5 kJ/mol for Ca 2 Tb 8 (SiO 4 ) 6 O 2 ; -643.3 ± 10.3 kJ/mol for Ca 2 Ho 8 (SiO 4 ) 6 O 2 ; and -403.2 ± 5.1 kJ/mol for Ca 2 Tm 8 (SiO 4 ) 6 O 2 . These thermodynamic parameters were used in assessing the thermochemical stability of these phases in the presence of water vapor from room temperature to 600 K, as encountered in the subsurface environments of a geological repository.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Role of mixed conducting Pr 0.1 Gd 0.1 Ce 0.8 O 1.9-δ barrier layer on the promotion of SOFC performance

The cathode activity in a solid oxide fuel cell can be promoted by introducing various catalysts to reduce its polarization resistance towards oxygen reduction, and thus improve cell performance. Here, in this work, the La 0.6 Sr 0.4 Co 0.2 Fe 0.8 O 3 (LSCF) cathode surface is modified by the infiltration of Pr 6 O 11 and the power density at 0.8 V and 750 °C is improved by 21%. Moreover, by replacing the traditional barrier layer Gd 0.2 Ce 0.8 O 1.9 with mixed conducting Pr 0.1 Gd 0.1 Ce 0.8 O 1.9 (PGCO), the power density increases by 38%. The ohmic resistance is dramatically reduced by applying the PGCO interlayer. The distribution of relaxation time was used to analyze the mechanism for which the polarization resistance was decreased, attributing to the mixed conduction nature in PrO x . An increase of power density, ~0.358 W/cm 2 (71%) at 0.8 V, is achieved with the implementation of both surface modification and buffer layer engineering.

08 HYDROGEN↗
DOE OSTI2021

Surface enhanced performance of La 0.6 Sr 0.4 Co 0.2 Fe 0.8 O 3-δ cathodes by infiltration Pr-Ni-Mn-O progress

Herein the present study reports the enhancement of electrochemical oxygen reduction activity of porous La 0.6 Sr 0.4 Co 0.2 Fe 0.8 O 3–δ (LSCF) cathodes by coating a thin film of Pr-Ni-Mn oxide (PNM5) using a multi-step infiltration process. XRD examination reveals that PNM5 mainly contains a multiphase mixture of Pr 6 O 11 , PrNiO 3 , MnO and NiO. SEM morphology shows a thin PNM5 film and small particles are formed on the surface of LSCF backbone particles. Impedance spectrum analysis indicates that PNM5 infiltrated LSCF exhibits dramatically reduced polarization resistance (R p ), reaching R p of 0.244 Ω cm 2 at 973 K, which is one-half of the baseline LSCF cathode. The activation energy of LSCF cathodes infiltrated with PNM5 is 1.45 eV, slightly lower than the baseline LSCF cathode (1.77 eV). Distribution of relaxation time (DRT) function analysis shows PNM5 infiltration layer significantly promotes the oxygen reduction reaction (ORR) of cathode surface. With the increase in firing temperature, the total resistance increases and R p changes from ion transport to oxygen reduction reaction. Degradation rate of the PNM5-infiltrated LSCF is also lower, 0.02168% vs 0.07093% for the baseline LSCF over a 200-h period. A single cell testing indicated that the peak power density of the PNM5-infiltrated cell was increased by 140.66%. Overall, PNM5 could be a potential catalyst for boosting the performance of a commercial LSCF cathode for solid oxide fuel cells (SOFC).

36 MATERIALS SCIENCE↗
DOE OSTI2020

High-pressure synthesis, crystal structure, and magnetic properties of the Shastry-Sutherland-lattice oxides BaL n 2 ZnO 5 (L n = Pr, Sm, Eu)

BaPr 2 ZnO 5 , BaSm 2 ZnO 5 , and BaEu 2 ZnO 5 – a series of 4f magnetic insulators comprising the Shastry-Sutherland lattice – were synthesized via a solid-state reaction under high-pressure and high-temperature conditions. The magnetic behaviors are well characterized by the localized 4f electrons of each Ln 3+ (= Pr, Sm, Eu) under the influence of the crystal-electric field of the surrounding ions. The magnetic susceptibility and heat capacity measurements of BaPr 2 ZnO 5 (Pr 3+ ; 4f 2 3 H 4 ) indicate the splitting of the ground state J-multiplet due to the crystal-electric field. BaSm 2 ZnO 5 (Sm 3+ ; 4f 5 6 H 5/2 ) is a strong Van Vleck paramagnet, while BaEu 2 ZnO 5 is non-magnetic due to the 7 F 0 ground state (Eu 3+ ; 4f 6 7 F 0 ). The series of new oxides enriches a group of the Shastry-Sutherland lattice materials and helps to develop a range of two-dimensional quantum materials.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Synthesis, crystal structure and magnetic properties of K Ln Se 2 ( Ln = La, Ce, Pr, Nd) structures: A family of 2D triangular lattice frustrated magnets

Here, we report the detail synthesis, single crystal structure characterization and magnetic properties of KLnSe 2 series obtained via solid state molten flux growth method. The crystal structures were characterized using single crystal x-ray diffraction. The KLnSe 2 (Ln = La, Ce, Pr and Nd) series crystallizes in the trigonal crystal system with the space group of R-3m (No. 166). The overall structure contains two-dimensional (2D) layers made from edged shared LnSe 6 -octahedra. Ln 3+ ions form a perfect triangular magnetic lattice which propagates along ab-plane. These triangular lattices are separated by the K + ions. The magnetic properties confirm that, Ce, Pr and Nd do not show any long-range ordering down to 0.4 K indicating frustrated magnetism in the KLnSe 2 series.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2026

Electro-chemo-mechanically Driven Ni Exsolution from (Pr,Ce,Ni)O 2−δ : Controlled Nucleation Density and Enhanced Electrode Kinetics

In situ exsolution of metal nanoparticles is a promising strategy to prepare electrocatalysts with enhanced activity and resistance to agglomeration for efficient chemical transformations and energy conversion. Achieving a high nucleation density of nanoparticles under mild conditions and understanding how to tailor the process is important for performance of these electrodes in electrochemical cells. In this work, we demonstrate facile exsolution of Ni nanoparticles using fluorite-structured (Pr,Ce)O 2−δ as the support oxide, driven by electrochemical potential and aided by the metastability of Ni in the solid solution (elastic driving force). We prepare single-phase oriented thin films of (Pr,Ce,Ni)O 2−δ (NPCO) on (Zr,Y)O 2−δ (YSZ) substrates by pulsed laser deposition. With the aid of a high-throughput electrochemical cell that provides a lateral gradient in Nernst voltage, we apply in situ near-ambient pressure synchrotron X-ray photoelectron spectroscopy and ex situ atomic force microscopy to investigate the impact of electrochemical potential on Ni nucleation density. We find that metallic Ni can be successfully exsolved at 550 °C upon cathodic biasing in 20 mTorr O 2 , and its nucleation density increases with increasing electrochemical driving force/decreasing oxygen chemical potential. We further evaluate the electrochemical performance under highly reducing (fuel electrode) conditions by electrochemical impedance spectroscopy. With the exsolved Ni nanoparticles, the surface exchange coefficient of the NPCO is found to be ∼4× higher than for PCO without exsolution. This work confirms mixed conducting fluorites as beneficial host lattices for facile transition-metal exsolution and suggests the possibility for constructing an all ceria-based electrochemical cell with PCO serving as both the cathode and the anode.

36 MATERIALS SCIENCE↗
DOE OSTI2021

A series of Rb 4 Ln 2 (P 2 S 6 )(PS 4 ) 2 (Ln = La, Ce, Pr, Nd, Sm, Gd) rare earth thiophosphates with two distinct thiophosphate units [P V S 4 ] 3- and [P IV 2 S 6 ] 4-

A series of rubidium rare earth thiophosphates with the formula Rb 4 Ln 2 (P 2 S 6 )(PS 4 ) 2 (Ln = La, Ce, Pr, Nd, Sm, and Gd) were synthesized using the high temperature molten flux crystal growth method utilizing a RbBr flux. Single crystals of all title compounds, as well as phase pure powders of the La-, Ce-, and Sm-containing compositions, were obtained. Single crystals of the title compounds were characterized by single crystal and powder X-ray diffraction for structure and phase identification. Rb 4 Ln 2 (P 2 S 6 )(PS 4 ) 2 crystallizes in the monoclinic crystal system adopting the P2 1 /n space group for the large rare earths (Ln = La, Ce, Pr) and the C2/c space group for the smaller rare earths (Ln = Nd, Sm, Gd). This Rb 4 Ln 2 (P 2 S 6 )(PS 4 ) 2 series is a rare example of thiophosphates containing both tetrahedral [P V S 4 ] 3– and dimeric [P IV 2 S 6 ] 4– thiophosphate units that, in this structural family, link corrugated rare earth sulfide chains into sheets. Here, the band gaps of the materials were determined from UV–Vis data and the fluorescence spectrum of Rb 4 Ce 2 (P 2 S 6 )(PS 4 ) 2 was collected. Optical band gaps were estimated to be 2.9 and 2.4 for the Nd and Sm analogues, respectively.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2023

Boosting the performance of reversible solid oxide electrochemical cells with a novel hybrid oxygen electrode, Pr 1.39 Ba 0.14 Sr 0.53 Co 1.48 Fe 0.76 O 6- δ -Ba 0.66 Sr 0.34 CoO 3- δ

Solid oxide electrochemical cells (SOECs) stand out as a highly promising clean energy technology that offers several benefits, showing significant potential to play a pivotal role in the transition towards a sustainable and low-carbon energy future. SOECs can efficiently convert the chemical energy stored in fuels to electricity in fuel cell mode, and produce various chemicals from abundant feedstocks (e.g., CO 2 , H 2 O) and intermittent solar/wind-based renewable electricity. Despite extensive efforts that have been devoted to designing novel materials and optimizing SOEC manufacturing processes, aiming to achieve enhanced energy efficiency, the current SOECs still suffer from poor performance, which is mainly due to the sluggish oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) kinetics. To address this challenge, in this work, we have successfully designed an in situ formed hybrid oxygen electrode material (Pr 1.39 Ba 0.14 Sr 0.53 Co 1.48 Fe 0.76 O 6- δ -Ba 0.66 Sr 0.34 CoO 3- δ ), which significantly improves the surface oxygen exchange coefficient and bulk oxygen-ion diffusion coefficient, enhancing the OER and ORR electrocatalytic activities. Further, the SOECs equipped with this newly developed oxygen electrode achieved exceptional performance for power generation using both hydrogen and propane as the fuels. At 750 °C, a peak power density of 2.4 W cm -2 was obtained with H 2 as the fuel. Additionally, the SOECs attain unprecedented performance in steam electrolysis mode. A current density of 4.4 A cm -2 was achieved at 1.3 V and 750 °C, which represents the highest performance among all yttria-stabilized zirconia (YSZ) electrolyte-based SOECs. The SOECs also deliver remarkable stability during the accelerated stability testing, highlighting the great potential of Pr 1.39 Ba 0.14 Sr 0.53 Co 1.48 Fe 0.76 O 6- δ -Ba 0.66 Sr 0.34 CoO 3- δ as a high-performance oxygen electrode for next generation SOECs.

08 HYDROGEN↗
DOE OSTI2020

Enhancement in hard magnetic properties of (Nd, Pr)–Fe–B melt-spun ribbons

The coercivity of RE 2 Fe 14 B-type permanent magnets is strongly influenced by the microstructural features such as grain boundary (GB) phases as well as grain sizes. Here, we have combined micromagnetic simulations and experiments to elucidate the role of excess RE (Nd/Pr) in determining the resulting hard magnetic properties of Nd–Pr–Fe–B melt-spun ribbons. The intrinsic coercivity (H c ) at room temperature significantly enhanced from 9.7 kOe to 15.3 kOe with the increase in the Nd/Pr content. Furthermore, the effect of non-magnetic grain refining refractory carbide (TiC) on both the microstructure and magnetic hardening was studied. The addition of TiC showed a very high coercivity H c of up to 19.0 kOe at room temperature. Micromagnetic simulation indicates that the coercivity enhancement is mainly due to the reduction of inter-grain magnetic interaction, which is due to the RE-rich nonmagnetic grain boundary (GB) phase and/or TiC distributed at the GB. This work provides useful information on the roles of non-magnetic grain boundary phases for improving the coercivity of Nd–Pr–Fe–B magnets. Combined with experimental and modeling results, we have discussed the mechanism responsible for the enhancements in coercivity and the suitability of the alloys for high-performance permanent magnet development.

36 MATERIALS SCIENCE↗
DOE OSTI2024

Local lattice distortions and electronic phases in perovskite manganite Pr 0.5 Sr 0.5 MnO 3

We use variable temperature and magnetic field total x-ray scattering to study the crystal structure of the strongly correlated Pr 0.5 Sr 0.5 MnO 3 perovskite, which is a paramagnetic insulator at room temperature, becomes a ferromagnetic metal at 272 K and, upon further decreasing the temperature, turns into an antiferromagnetic insulator at 105 K. We find that a model featuring a monoclinic symmetry captures the structure and its temperature and field evolution well, eliminating the need to evoke a phase segregation scenario as done in prior studies. It appears that coupled variations in Mn–oxygen bonding distances and angles from their values in an undistorted perovskite lattice, i.e., coupled local lattice distortions, assist the phase transitions in Pr 0.5 Sr 0.5 MnO 3 , contributing to its unique physical properties. Local structural distortions thus emerge as an important degree of freedom in strongly correlated systems, in particular perovskite manganates, and, therefore, they should be fully accounted for when their fascinating physics is considered.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Spontaneous Hall effect enhanced by local Ir moments in epitaxial Pr 2 Ir 2 O 7 thin films

Rare-earth pyrochlore iridates ( RE 2 Ir 2 O 7 ) consist of two interpenetrating cation sublattices, the RE with highly frustrated magnetic moments, and the iridium with extended conduction orbitals significantly mixed by spin-orbit interactions. The coexistence and coupling of these two sublattices create a landscape for discovery and manipulation of quantum phenomena such as the topological Hall effect, massless conduction bands, and quantum criticality. Thin films allow extended control of the material system via symmetry-lowering effects such as strain. While bulk Pr 2 Ir 2 O 7 shows a spontaneous hysteretic Hall effect below 1.5 K, we observe the effect at elevated temperatures up to 15 K in epitaxial thin films on (111) yttria-stabilized zirconia (YSZ) substrates synthesized via solid-phase epitaxy. Similar to the bulk, the lack of observable long-range magnetic order in the thin films points to a topological origin. We use synchrotron-based element-specific x-ray diffraction and x-ray magnetic circular dichroism to compare powders and thin films to attribute the spontaneous Hall effect in the films to localization of the Ir moments. Further, we link the thin-film Ir local moments to lattice distortions absent in the bulklike powders. We conclude that the elevated-temperature spontaneous Hall effect is caused by the topological effect originating either from the Ir or Pr sublattice, with interaction strength enhanced by the Ir local moments. This spontaneous Hall effect with weak net moment highlights the effect of vanishingly small lattice distortions as a means to discover topological phenomena in metallic frustrated magnetic materials.

36 MATERIALS SCIENCE↗