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All sourcesNASA NTRSDOE OSTI
NASA NTRS2009

Application of TRMM PR and TMI Measurements to Assess Cloud Microphysical Schemes in the MM5 Model for a Winter Storm

Seen by the human eye, precipitation particles are commonly drops of rain, flakes of snow, or lumps of hail that reach the ground. Remote sensors and numerical models usually deal with information about large collections of rain, snow, and hail (or graupel --also called soft hail ) in a volume of air. Therefore, the size and number of the precipitation particles and how particles interact, evolve, and fall within the volume of air need to be represented using physical laws and mathematical tools, which are often implemented as cloud and precipitation microphysical parameterizations in numerical models. To account for the complexity of the precipitation physical processes, scientists have developed various types of such schemes in models. The accuracy of numerical weather forecasting may vary dramatically when different types of these schemes are employed. Therefore, systematic evaluations of cloud and precipitation schemes are of great importance for improvement of weather forecasts. This study is one such endeavor; it pursues quantitative assessment of all the available cloud and precipitation microphysical schemes in a weather model (MM5) through comparison with the observations obtained by National Aeronautics and Space Administration (NASA) s and Japan Aerospace Exploration Agency (JAXA) s Tropical Rainfall Measuring Mission (TRMM) precipitation radar (PR) and microwave imager (TMI). When satellite sensors (like PR or TMI) detect information from precipitation particles, they cannot directly observe the microphysical quantities (e.g., water species phase, density, size, and amount etc.). Instead, they tell how much radiation is absorbed by rain, reflected away from the sensor by snow or graupel, or reflected back to the satellite. On the other hand, the microphysical quantities in the model are usually well represented in microphysical schemes and can be converted to radiative properties that can be directly compared to the corresponding PR and TMI observations. This study employs this method to evaluate the accuracy of the simulated radiative properties by the MM5 model with different microphysical schemes. It is found that the representations of particle density, size, and mass in the different schemes in the MM5 model determine the model s performance when predicting a winter storm over the eastern Pacific Ocean. Schemes lacking moderate density particles (i.e. graupel), with snow flakes that are too large, or with excessive mass of snow or graupel lead to degraded prediction of the radiative properties as observed by the TRMM satellite. This study demonstrates the uniqueness of the combination of both an active microwave sensor (PR) and passive microwave sensor (TMI) onboard TRMM on assessing the accuracy of numerical weather forecasting. It improves our understanding of the physical and radiative properties of different types of precipitation particles and provides suggestions for better representation of cloud and precipitation processes in numerical models. It would, ultimately, contribute to answering questions like "Why did it not rain when the forecast says it would?"

Han, Mei↗
DOE OSTI2020

Materials Data on Pr(AlSi)2 by Materials Project

PrAl2Si2 crystallizes in the trigonal P-3m1 space group. The structure is three-dimensional. Pr is bonded to six equivalent Si atoms to form distorted PrSi6 octahedra that share corners with twelve equivalent AlSi4 tetrahedra, edges with six equivalent PrSi6 octahedra, and edges with six equivalent AlSi4 tetrahedra. All Pr–Si bond lengths are 3.08 Å. Al is bonded to four equivalent Si atoms to form distorted AlSi4 tetrahedra that share corners with six equivalent PrSi6 octahedra, corners with six equivalent AlSi4 tetrahedra, edges with three equivalent PrSi6 octahedra, and edges with three equivalent AlSi4 tetrahedra. The corner-sharing octahedra tilt angles range from 23–53°. There are three shorter (2.53 Å) and one longer (2.54 Å) Al–Si bond lengths. Si is bonded to three equivalent Pr and four equivalent Al atoms to form a mixture of distorted edge and corner-sharing SiPr3Al4 pentagonal bipyramids.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Pr(MnGe)2 by Materials Project

PrMn2Ge2 crystallizes in the tetragonal I4/mmm space group. The structure is three-dimensional. Pr is bonded in a 8-coordinate geometry to eight equivalent Ge atoms. All Pr–Ge bond lengths are 3.17 Å. Mn is bonded to four equivalent Ge atoms to form a mixture of corner and edge-sharing MnGe4 tetrahedra. All Mn–Ge bond lengths are 2.45 Å. Ge is bonded in a 9-coordinate geometry to four equivalent Pr, four equivalent Mn, and one Ge atom. The Ge–Ge bond length is 2.76 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Pr(ReO4)2 by Materials Project

Pr(ReO4)2 crystallizes in the trigonal P-3 space group. The structure is two-dimensional and consists of one Pr(ReO4)2 sheet oriented in the (0, 0, 1) direction. Pr3+ is bonded to six equivalent O2- atoms to form PrO6 octahedra that share corners with six equivalent ReO4 tetrahedra. All Pr–O bond lengths are 2.39 Å. Re+6.50+ is bonded to four O2- atoms to form ReO4 tetrahedra that share corners with three equivalent PrO6 octahedra. The corner-sharing octahedral tilt angles are 20°. There is one shorter (1.74 Å) and three longer (1.78 Å) Re–O bond length. There are two inequivalent O2- sites. In the first O2- site, O2- is bonded in a distorted bent 150 degrees geometry to one Pr3+ and one Re+6.50+ atom. In the second O2- site, O2- is bonded in a single-bond geometry to one Re+6.50+ atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Pr(AlBr4)3 by Materials Project

Pr(AlBr4)3 crystallizes in the trigonal P3_121 space group. The structure is one-dimensional and consists of one Pr(AlBr4)3 ribbon oriented in the (0, 0, 1) direction. Pr3+ is bonded in a 8-coordinate geometry to eight Br1- atoms. There are a spread of Pr–Br bond distances ranging from 3.00–3.17 Å. There are two inequivalent Al3+ sites. In the first Al3+ site, Al3+ is bonded in a tetrahedral geometry to four Br1- atoms. There are a spread of Al–Br bond distances ranging from 2.27–2.41 Å. In the second Al3+ site, Al3+ is bonded in a tetrahedral geometry to four Br1- atoms. There are two shorter (2.33 Å) and two longer (2.34 Å) Al–Br bond lengths. There are six inequivalent Br1- sites. In the first Br1- site, Br1- is bonded in an L-shaped geometry to one Pr3+ and one Al3+ atom. In the second Br1- site, Br1- is bonded in a distorted L-shaped geometry to one Pr3+ and one Al3+ atom. In the third Br1- site, Br1- is bonded in a single-bond geometry to one Al3+ atom. In the fourth Br1- site, Br1- is bonded in a distorted L-shaped geometry to one Pr3+ and one Al3+ atom. In the fifth Br1- site, Br1- is bonded in a single-bond geometry to one Al3+ atom. In the sixth Br1- site, Br1- is bonded in a distorted L-shaped geometry to one Pr3+ and one Al3+ atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Pr(HO)3 by Materials Project

Pr(OH)3 crystallizes in the monoclinic Pm space group. The structure is three-dimensional. there are two inequivalent Pr3+ sites. In the first Pr3+ site, Pr3+ is bonded in a 9-coordinate geometry to nine O2- atoms. There are a spread of Pr–O bond distances ranging from 2.54–2.62 Å. In the second Pr3+ site, Pr3+ is bonded in a 9-coordinate geometry to nine O2- atoms. There are a spread of Pr–O bond distances ranging from 2.53–2.66 Å. There are six inequivalent H1+ sites. In the first H1+ site, H1+ is bonded in a single-bond geometry to one O2- atom. The H–O bond length is 0.98 Å. In the second H1+ site, H1+ is bonded in a single-bond geometry to one O2- atom. The H–O bond length is 0.97 Å. In the third H1+ site, H1+ is bonded in a single-bond geometry to one O2- atom. The H–O bond length is 0.97 Å. In the fourth H1+ site, H1+ is bonded in a single-bond geometry to one O2- atom. The H–O bond length is 0.98 Å. In the fifth H1+ site, H1+ is bonded in a single-bond geometry to one O2- atom. The H–O bond length is 0.97 Å. In the sixth H1+ site, H1+ is bonded in a single-bond geometry to one O2- atom. The H–O bond length is 0.97 Å. There are six inequivalent O2- sites. In the first O2- site, O2- is bonded in a single-bond geometry to three Pr3+ and one H1+ atom. In the second O2- site, O2- is bonded in a single-bond geometry to three Pr3+ and one H1+ atom. In the third O2- site, O2- is bonded in a single-bond geometry to three Pr3+ and one H1+ atom. In the fourth O2- site, O2- is bonded in a single-bond geometry to three Pr3+ and one H1+ atom. In the fifth O2- site, O2- is bonded in a single-bond geometry to three Pr3+ and one H1+ atom. In the sixth O2- site, O2- is bonded in a single-bond geometry to three Pr3+ and one H1+ atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Pr(FeSb3)5 by Materials Project

Pr(FeSb3)5 crystallizes in the trigonal R-3 space group. The structure is three-dimensional. there are two inequivalent Pr3+ sites. In the first Pr3+ site, Pr3+ is bonded to twelve Sb+1.20- atoms to form PrSb12 cuboctahedra that share faces with eight FeSb6 octahedra. There are six shorter (3.41 Å) and six longer (3.42 Å) Pr–Sb bond lengths. In the second Pr3+ site, Pr3+ is bonded to twelve Sb+1.20- atoms to form PrSb12 cuboctahedra that share faces with eight FeSb6 octahedra. There are three shorter (3.40 Å) and nine longer (3.41 Å) Pr–Sb bond lengths. There are six inequivalent Fe3+ sites. In the first Fe3+ site, Fe3+ is bonded to six Sb+1.20- atoms to form FeSb6 octahedra that share corners with six FeSb6 octahedra and a faceface with one PrSb12 cuboctahedra. The corner-sharing octahedra tilt angles range from 51–52°. There are three shorter (2.52 Å) and three longer (2.56 Å) Fe–Sb bond lengths. In the second Fe3+ site, Fe3+ is bonded to six Sb+1.20- atoms to form FeSb6 octahedra that share corners with six FeSb6 octahedra and faces with two equivalent PrSb12 cuboctahedra. The corner-sharing octahedral tilt angles are 52°. There are four shorter (2.54 Å) and two longer (2.55 Å) Fe–Sb bond lengths. In the third Fe3+ site, Fe3+ is bonded to six Sb+1.20- atoms to form FeSb6 octahedra that share corners with six FeSb6 octahedra and faces with two PrSb12 cuboctahedra. The corner-sharing octahedral tilt angles are 52°. There are three shorter (2.54 Å) and three longer (2.55 Å) Fe–Sb bond lengths. In the fourth Fe3+ site, Fe3+ is bonded to six Sb+1.20- atoms to form FeSb6 octahedra that share corners with six FeSb6 octahedra and a faceface with one PrSb12 cuboctahedra. The corner-sharing octahedra tilt angles range from 51–52°. There are three shorter (2.52 Å) and three longer (2.56 Å) Fe–Sb bond lengths. In the fifth Fe3+ site, Fe3+ is bonded to six Sb+1.20- atoms to form FeSb6 octahedra that share corners with six FeSb6 octahedra and faces with two PrSb12 cuboctahedra. The corner-sharing octahedral tilt angles are 52°. There are four shorter (2.54 Å) and two longer (2.55 Å) Fe–Sb bond lengths. In the sixth Fe3+ site, Fe3+ is bonded to six equivalent Sb+1.20- atoms to form FeSb6 octahedra that share corners with six equivalent FeSb6 octahedra and faces with two equivalent PrSb12 cuboctahedra. The corner-sharing octahedral tilt angles are 52°. All Fe–Sb bond lengths are 2.54 Å. There are nine inequivalent Sb+1.20- sites. In the first Sb+1.20- site, Sb+1.20- is bonded in a 2-coordinate geometry to one Pr3+ and two Fe3+ atoms. In the second Sb+1.20- site, Sb+1.20- is bonded in a 2-coordinate geometry to one Pr3+ and two Fe3+ atoms. In the third Sb+1.20- site, Sb+1.20- is bonded in a 2-coordinate geometry to two equivalent Fe3+ atoms. In the fourth Sb+1.20- site, Sb+1.20- is bonded in a 2-coordinate geometry to one Pr3+ and two Fe3+ atoms. In the fifth Sb+1.20- site, Sb+1.20- is bonded in a 2-coordinate geometry to one Pr3+ and two Fe3+ atoms. In the sixth Sb+1.20- site, Sb+1.20- is bonded in a 2-coordinate geometry to one Pr3+ and two Fe3+ atoms. In the seventh Sb+1.20- site, Sb+1.20- is bonded in a 2-coordinate geometry to one Pr3+, two Fe3+, and one Sb+1.20- atom. The Sb–Sb bond length is 3.03 Å. In the eighth Sb+1.20- site, Sb+1.20- is bonded in a 2-coordinate geometry to one Pr3+, two Fe3+, and one Sb+1.20- atom. The Sb–Sb bond length is 2.99 Å. In the ninth Sb+1.20- site, Sb+1.20- is bonded in a 2-coordinate geometry to one Pr3+, two Fe3+, and two Sb+1.20- atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Pr(NiO3)2 by Materials Project

Pr(NiO3)2 crystallizes in the triclinic P1 space group. The structure is three-dimensional. there are two inequivalent Pr4+ sites. In the first Pr4+ site, Pr4+ is bonded in a 9-coordinate geometry to nine O2- atoms. There are a spread of Pr–O bond distances ranging from 2.41–2.74 Å. In the second Pr4+ site, Pr4+ is bonded in a 9-coordinate geometry to nine O2- atoms. There are a spread of Pr–O bond distances ranging from 2.40–2.76 Å. There are four inequivalent Ni4+ sites. In the first Ni4+ site, Ni4+ is bonded to six O2- atoms to form corner-sharing NiO6 octahedra. The corner-sharing octahedra tilt angles range from 12–22°. There are a spread of Ni–O bond distances ranging from 1.83–1.87 Å. In the second Ni4+ site, Ni4+ is bonded to six O2- atoms to form corner-sharing NiO6 octahedra. The corner-sharing octahedra tilt angles range from 14–22°. There are a spread of Ni–O bond distances ranging from 1.97–2.04 Å. In the third Ni4+ site, Ni4+ is bonded to six O2- atoms to form corner-sharing NiO6 octahedra. The corner-sharing octahedra tilt angles range from 13–21°. There are a spread of Ni–O bond distances ranging from 1.83–1.87 Å. In the fourth Ni4+ site, Ni4+ is bonded to six O2- atoms to form corner-sharing NiO6 octahedra. The corner-sharing octahedra tilt angles range from 12–21°. There are a spread of Ni–O bond distances ranging from 1.96–2.04 Å. There are twelve inequivalent O2- sites. In the first O2- site, O2- is bonded in a distorted T-shaped geometry to one Pr4+ and two Ni4+ atoms. In the second O2- site, O2- is bonded in a 3-coordinate geometry to one Pr4+ and two Ni4+ atoms. In the third O2- site, O2- is bonded in a distorted T-shaped geometry to one Pr4+ and two Ni4+ atoms. In the fourth O2- site, O2- is bonded in a 4-coordinate geometry to two Pr4+ and two Ni4+ atoms. In the fifth O2- site, O2- is bonded in a 4-coordinate geometry to two Pr4+ and two Ni4+ atoms. In the sixth O2- site, O2- is bonded in a 4-coordinate geometry to two equivalent Pr4+ and two Ni4+ atoms. In the seventh O2- site, O2- is bonded in a distorted T-shaped geometry to one Pr4+ and two Ni4+ atoms. In the eighth O2- site, O2- is bonded in a distorted T-shaped geometry to one Pr4+ and two Ni4+ atoms. In the ninth O2- site, O2- is bonded in a distorted T-shaped geometry to one Pr4+ and two Ni4+ atoms. In the tenth O2- site, O2- is bonded in a 4-coordinate geometry to two Pr4+ and two Ni4+ atoms. In the eleventh O2- site, O2- is bonded in a 4-coordinate geometry to two Pr4+ and two Ni4+ atoms. In the twelfth O2- site, O2- is bonded in a 4-coordinate geometry to two equivalent Pr4+ and two Ni4+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Pr(Ge3Pt)4 by Materials Project

PrPt4Ge12 crystallizes in the cubic Im-3 space group. The structure is three-dimensional. Pr is bonded to twelve equivalent Ge atoms to form PrGe12 cuboctahedra that share faces with eight equivalent PtGe6 octahedra. All Pr–Ge bond lengths are 3.36 Å. Pt is bonded to six equivalent Ge atoms to form PtGe6 octahedra that share corners with six equivalent PtGe6 octahedra and faces with two equivalent PrGe12 cuboctahedra. The corner-sharing octahedral tilt angles are 60°. All Pt–Ge bond lengths are 2.52 Å. Ge is bonded in a 2-coordinate geometry to one Pr, two equivalent Pt, and two equivalent Ge atoms. There are one shorter (2.54 Å) and one longer (2.65 Å) Ge–Ge bond lengths.

36 MATERIALS SCIENCE↗
DOE OSTI2023

Development of Dy-free Nd-Fe-B-based sintered magnet through grain boundary engineering using Pr-Cu alloys

For this study, Dy-free sintered magnets were fabricated by mixing Nd-Fe-B powder with various amounts of Pr-Cu powder followed by the common procedures for making Nd-Fe-B based sintered magnets. With the Pr-Cu addition increasing from 0 to 10 wt.%, the obtained magnets’ H cj increases from the original 14.5 kOe to 18.6 kOe. The highest (BH) max achieved was 35.0 MGOe with 7.5 wt.% PrCu. The distribution of the Pr and Cu elements was primarily at grain boundary and triple junctions, leading to a reduced coupling among grains, thus an enhanced H cj .

36 MATERIALS SCIENCE↗
DOE OSTI2024

Enhancing Direct Electrochemical CO 2 Electrolysis by Introducing A-Site Deficiency for the Dual-Phase Pr(Ca)Fe(Ni)O 3-δ Cathode

High-temperature CO 2 electrolysis via solid oxide electrolysis cells (CO 2 –SOECs) has drawn special attention due to the high energy convention efficiency, fast electrode kinetics, and great potential in carbon cycling. However, the development of cathode materials with high catalytic activity and chemical stability for pure CO 2 electrolysis is still a great challenge. In this work, A-site cation deficient dual-phase material, namely (Pr 0.4 Ca 0.6 ) x Fe 0.8 Ni 0.2 O 3-δ (PCFN, x = 1, 0.95, and 0.9), has been designed as the fuel electrode for a pure CO 2 –SOEC, which presents superior electrochemical performance. Among all these compositions, (Pr 0.4 Ca 0.6 ) 0.95 Fe 0.8 Ni 0.2 O 3-δ (PCFN95) exhibited the lowest polarization resistance of 0.458 Ω cm 2 at open-circuit voltage and 800 °C. The application of PCFN95 as the cathode in a single cell yields an impressive electrolysis current density of 1.76 A cm -2 at 1.5 V and 800 °C, which is 76% higher than that of single cells with stoichiometric Pr 0.4 Ca 0.6 Fe 0.8 Ni 0.2 O 3-δ (PCFN100) cathode. The effects of A-site deficiency on materials' phase structure and physicochemical properties are also systematically investigated. Such an enhancement in electrochemical performance is attributed to the promotion of effective CO 2 adsorption, as well as the improved electrode kinetics resulting from the A-site deficiency.

30 DIRECT ENERGY CONVERSION↗
DOE OSTI2022

Magnetocaloric response with significant mechanical efficiency in frustrated intermetallic compound $\mathrm{Pr_{2}Co_{0.86}Si_{2.88}}$

We report magnetically frustrated materials are considered as a promising unconventional members of caloric materials. Here, the magnetocaloric properties of the frustrated Pr 2 Co 0.86 Si 2.88 have been investigated and discussed with the aid of density functional theory (DFT) calculations. The material exhibits a magnetic entropy change (-ΔS M ) of 13.1 J/kg-K for ΔH = 70 kOe around low-temperature transition T L ~ 4 K associated with the antiferromagnetic coupling between localized Pr-4f and itinerant Co-3d moments. Despite the absence of any long-range magnetic order, the obtained - ΔS M is one of the highest among the known Pr-based good magnetocaloric materials at cryogenic temperature range. It also exhibits a relative cooling power (RCP) of ~ 201 J/kg and an adiabatic temperature change of 6.3 K around T L at 70 kOe. Moreover, the compound also exhibits a high mechanical efficiency and moderate electrical efficiency, being beneficial for possible technological applications.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Ln 10 S 14 O (Ln = La, Pr, Nd, Sm) Oxysulfides: A Series of Direct n-Type Semiconductors

Lanthanoid oxysulfides are promising materials for technological applications owing to their magnetic, photoluminescent, catalytic, and optoelectronic properties. In this work, we report the solid-state synthesis and structural characterization of Ln 10 S 14 O (Ln = La, Ce, Pr, Nd, Sm) oxysulfides. Then, we present a thorough discussion on their electronic and photophysical properties. Through Tauc plot analysis and the derivation of the absorption spectrum fitting method (DASF), we determine that all oxysulfides have direct band gaps with energies of 2.84 eV (La), 2.02 eV (Ce), 2.56 eV (Pr), 2.64 eV (Nd), and 2.41 eV (Sm). Furthermore, surface photovoltage spectroscopy (SPS) shows photovoltage (ΔCPD) values of –0.4 to –1.1 V for La-, Pr-, Nd-, and Sm-containing compounds when illuminated near the optical band gap, indicating that these oxysulfides are n-type semiconductors, which is consistent with Mott–Schottky analysis. Photovoltages under sub-band gap illumination energy and photovoltage decay data suggest mid-band gap states possibly arising from the lanthanoid 4f orbitals and/or defects within the crystal structure or at the particle surfaces. These photophysical properties suggest possible applications of the oxysulfides in photoelectrochemical and photovoltaic energy conversion.

14 SOLAR ENERGY↗
DOE OSTI2020

Hydrolysis of Metal Dioxides Differentiates d-block from f-block Elements: Pa(V) as a 6d Transition Metal; Pr(V) as a 4f “Lanthanyl”

Gas-phase reactions of pentavalent metal dioxide cations M V O 2 + with water were studied experimentally for M = V, Nb, Ta, Pr, Pa, U, Pu, and Am. Addition of two H 2 O can occur by adsorption to yield hydrate (H 2 O) 2 M V O 2 + or by hydrolysis to yield hydroxide M V (OH) 4 + . Displacement of H 2 O by acetone indicates hydrates for Pr V , U V , Pu V , and Am V , whereas nondisplacement indicates hydroxides for Nb V , Ta V , and Pa V . Computed potential energy profiles agree with the experimental results and furthermore indicate that acetone unexpectedly induces dehydrolysis and displaces two H 2 O from (H 2 O)VO(OH) 2 + to yield (acetone) 2 VO 2 + . Structures and energies for several M V , as well as for Th IV and U VI , indicate that hydrolysis is governed by the involvement of valence f versus d orbitals in bonding: linear f-element dioxides are more resistant to hydrolysis than bent d-element dioxides. Accordingly, for early actinides, hydrolysis of Th IV is characteristic of a 6d-block transition metal; hydration of U V and U VI is characteristic of 5f actinyls; and Pa V is intermediate between 6d and 5f. The praseodymium oxide cation Pr V O 2 + is assigned as an actinyl-like lanthanyl with properties governed by 4f bonding.

36 MATERIALS SCIENCE↗
DOE OSTI2024

Facile Interfacial Reduction Suppresses Redox Chemical Expansion and Promotes the Polaronic to Ionic Transition in Mixed Conducting (Pr,Ce)O 2−δ Nanoparticles

Mixed ionic/electronic conductors (MIECs) are essential components of solid-state electrochemical devices, such as solid oxide fuel/electrolysis cells. For efficient performance, MIECs are typically nanostructured, to enhance the reaction kinetics. However, the effect of nanostructuring on MIEC chemo-mechanical coupling and transport properties, which also impact cell durability and efficiency, has not yet been well understood. Here, in this work, Pr 0.2 Ce 0.8 O 2−δ (PCO20) nanopowders were prepared by coprecipitation, then sintered in a modified dilatometer at three different temperatures (600, 725, and 850 °C) for microstructure evolution, resulting in three samples with different average particle sizes (23, 30, and 53 nm). The chemical strain and electronic/ionic conductivity were then measured simultaneously on stable nanostructures in four isotherms from 550 to 400 °C with steps in pO 2 (1 to 10 –4 atm O 2 ). A microcrystalline bar was prepared and measured for comparison. Particle size reduction led to a monotonically decreasing isothermal redox chemical strain, confirmed by in situ high-temperature, controlled-atmosphere XRD measurements. The corresponding conductivity measurements provided defect chemical insight into the particle size-dependent chemical expansion behavior. The significant weakening of the pO 2 dependence and decreased activation energy for electrical conduction with decreasing particle size indicated a decrease in the reduction enthalpy of PCO, shifting the transition from (Pr) polaronic to ionic behavior to higher pO 2 . STEM-EELS measurements confirmed the majority of Pr was reduced to 3+ in the nanoparticles, while Ce remained 4+. These results demonstrate suppression of deleterious chemical expansion and tailoring of the dominant charge carrier simply through controlling the particle size, providing insights for MIEC microstructural design.

ceria↗
DOE OSTI2022

Stabilization of three-dimensional charge order through interplanar orbital hybridization in Pr x Y 1–x Ba 2 Cu 3 O 6+δ

The shape of 3d-orbitals often governs the electronic and magnetic properties of correlated transition metal oxides. In the superconducting cuprates, the planar confinement of the d x 2 –y 2 orbital dictates the two-dimensional nature of the unconventional superconductivity and a competing charge order. Achieving orbital-specific control of the electronic structure to allow coupling pathways across adjacent planes would enable direct assessment of the role of dimensionality in the intertwined orders. Using Cu L 3 and Pr M 5 resonant x-ray scattering and first-principles calculations, we report a highly correlated three-dimensional charge order in Pr-substituted YBa 2 Cu 3 O 7 , where the Pr f-electrons create a direct orbital bridge between CuO 2 planes. With this we demonstrate that interplanar orbital engineering can be used to surgically control electronic phases in correlated oxides and other layered materials.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2020

Distinctive exchange bias and unusual memory effects in magnetically compensated Pr 0.75 Gd 0.25 ScGe

Tuning the chemistry of materials often leads to discoveries of interesting phenomena that expand basic science and support practical applications. Here we show how different spin–orbit coupling in light and heavy lanthanides can be exploited to create complex magnetic ground states and thereby unusual spontaneous exchange bias (SEB), conventional exchange bias (CEB), and magnetic memory effects in almost ideally magnetically compensated Pr 0.75 Gd 0.25 ScGe, which is a representative of the PrScGe–GdScGe solid solution. We report the synthesis and detailed characterization of Pr 0.75 Gd 0.25 ScGe by X-ray powder diffraction, scanning electron microscopy, and magnetization measurements in magnetic fields up to 140 kOe. Partial substitution of a light lanthanide, Pr, with a heavy lanthanide, Gd, results in a complex magnetic ground state, which includes large spontaneous and conventional exchange biases reaching magnitudes of ~1.7 kOe and ~3.5 kOe, respectively, at T = 2 K, as well as shape dependent magnetic compensation and bias phenomena occurring in small external fields.

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

Synthesis of a series of rare-earth-based multi-anion chalcogenide iodides RE 3 Si 2 Se x S 8− x I (RE = La, Ce, Pr, and Nd) using the flux-assisted boron–chalcogen mixture method

Single crystals and polycrystalline powders of rare earth mixed chalcogenide iodides La 3 Si 2 Se 1.21 S 6.79 I, Ce 3 Si 2 Se 1.39 S 6.61 I, Pr 3 Si 2 Se 1.22 S 6.78 I, and Nd 3 Si 2 Se 1.18 S 6.82 I were prepared using the reactive flux-assisted boron–chalcogen mixture (BCM) method at 850 °C. All compounds crystallized in the monoclinic crystal system, space group C2/c (space group number 15). The series adopts the La 3 Si 2 O 8 Cl structure type, containing isolated SiQ 4 tetrahedra connected by REQ 8 (RE = La, Ce, Pr and Nd) polyhedra; this arrangement creates tunnels that are filled by I atoms. The partial substitution of S by Se was carried out to modulate the optical properties. Phase pure samples and uniform solid solutions were obtained for all compositions as determined using powder X-ray diffraction patterns. Polycrystalline powders were used for physical property measurements, including magnetic susceptibility and UV-Vis diffuse reflectance. The solid-state UV-Vis data for the polycrystalline La 3 Si 2 Se 1.21 S 6.79 I, Ce 3 Si 2 Se 1.39 S 6.61 I, and Pr 3 Si 2 Se 1.22 S 6.78 I samples revealed band gaps of E g = 2.5(1), 2.2(1), and 2.3(1) eV, typical of semiconductors. Magnetic measurements indicated that Ce 3 Si 2 Se 1.39 S 6.61 I and Nd 3 Si 2 Se 1.18 S 6.82 I exhibit paramagnetic behavior with slightly negative Weiss constants θ = −25 and −38. The photoluminescence spectrum of Ce 3 Si 2 Se 1.39 S 6.61 I exhibits a broad emission band around ∼493 nm.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗