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

Materials Data on Pr(TmS2)3 by Materials Project

Pr(TmS2)3 crystallizes in the monoclinic P2_1/m space group. The structure is three-dimensional. there are three inequivalent Tm3+ sites. In the first Tm3+ site, Tm3+ is bonded to seven S2- atoms to form distorted TmS7 pentagonal bipyramids that share corners with three TmS6 octahedra, edges with two equivalent TmS6 octahedra, and edges with four equivalent TmS7 pentagonal bipyramids. The corner-sharing octahedra tilt angles range from 39–51°. There are a spread of Tm–S bond distances ranging from 2.67–2.90 Å. In the second Tm3+ site, Tm3+ is bonded to six S2- atoms to form TmS6 octahedra that share corners with three equivalent TmS6 octahedra, a cornercorner with one TmS7 pentagonal bipyramid, edges with four equivalent TmS6 octahedra, and edges with two equivalent TmS7 pentagonal bipyramids. The corner-sharing octahedra tilt angles range from 55–61°. There are a spread of Tm–S bond distances ranging from 2.65–2.76 Å. In the third Tm3+ site, Tm3+ is bonded to six S2- atoms to form TmS6 octahedra that share corners with three equivalent TmS6 octahedra, corners with two equivalent TmS7 pentagonal bipyramids, and edges with four equivalent TmS6 octahedra. The corner-sharing octahedra tilt angles range from 55–61°. There are a spread of Tm–S bond distances ranging from 2.64–2.77 Å. Pr3+ is bonded in a 8-coordinate geometry to eight S2- atoms. There are a spread of Pr–S bond distances ranging from 2.91–3.04 Å. There are six inequivalent S2- sites. In the first S2- site, S2- is bonded in a 4-coordinate geometry to four Tm3+ atoms. In the second S2- site, S2- is bonded to three Tm3+ and one Pr3+ atom to form distorted SPrTm3 trigonal pyramids that share corners with two equivalent SPr2Tm3 square pyramids, corners with four SPr2Tm3 trigonal bipyramids, corners with two equivalent SPrTm3 trigonal pyramids, edges with three equivalent SPr2Tm3 square pyramids, and edges with two equivalent SPr3Tm2 trigonal bipyramids. In the third S2- site, S2- is bonded in a rectangular see-saw-like geometry to four Tm3+ atoms. In the fourth S2- site, S2- is bonded to three equivalent Tm3+ and two equivalent Pr3+ atoms to form distorted SPr2Tm3 square pyramids that share corners with six SPr2Tm3 trigonal bipyramids, corners with two equivalent SPrTm3 trigonal pyramids, edges with four equivalent SPr2Tm3 square pyramids, edges with two SPr2Tm3 trigonal bipyramids, and edges with three equivalent SPrTm3 trigonal pyramids. In the fifth S2- site, S2- is bonded to three Tm3+ and two equivalent Pr3+ atoms to form distorted SPr2Tm3 trigonal bipyramids that share corners with two equivalent SPr2Tm3 square pyramids, corners with two equivalent SPr3Tm2 trigonal bipyramids, corners with three equivalent SPrTm3 trigonal pyramids, an edgeedge with one SPr2Tm3 square pyramid, and edges with five SPr2Tm3 trigonal bipyramids. In the sixth S2- site, S2- is bonded to two equivalent Tm3+ and three equivalent Pr3+ atoms to form distorted SPr3Tm2 trigonal bipyramids that share corners with four equivalent SPr2Tm3 square pyramids, corners with two equivalent SPr2Tm3 trigonal bipyramids, a cornercorner with one SPrTm3 trigonal pyramid, an edgeedge with one SPr2Tm3 square pyramid, edges with seven SPr2Tm3 trigonal bipyramids, and edges with two equivalent SPrTm3 trigonal pyramids.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Pr(PPt)2 by Materials Project

Pr(PtP)2 crystallizes in the tetragonal I4/mmm space group. The structure is three-dimensional. Pr3+ is bonded in a 8-coordinate geometry to eight P3- atoms. There are four shorter (3.23 Å) and four longer (3.24 Å) Pr–P bond lengths. There are two inequivalent Pt+1.50+ sites. In the first Pt+1.50+ site, Pt+1.50+ is bonded in a 5-coordinate geometry to five P3- atoms. There are one shorter (2.40 Å) and four longer (2.42 Å) Pt–P bond lengths. In the second Pt+1.50+ site, Pt+1.50+ is bonded in a distorted rectangular see-saw-like geometry to four equivalent P3- atoms. All Pt–P bond lengths are 2.54 Å. There are two inequivalent P3- sites. In the first P3- site, P3- is bonded in a 10-coordinate geometry to four equivalent Pr3+, five Pt+1.50+, and one P3- atom. The P–P bond length is 2.69 Å. In the second P3- site, P3- is bonded in a 8-coordinate geometry to four equivalent Pr3+ and four equivalent Pt+1.50+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Pr(CrB3)2 by Materials Project

Pr(CrB3)2 crystallizes in the orthorhombic Immm space group. The structure is three-dimensional. Pr3+ is bonded in a 12-coordinate geometry to sixteen B2- atoms. There are a spread of Pr–B bond distances ranging from 2.85–2.96 Å. Cr+4.50+ is bonded in a 10-coordinate geometry to ten B2- atoms. There are a spread of Cr–B bond distances ranging from 2.14–2.23 Å. There are two inequivalent B2- sites. In the first B2- site, B2- is bonded in a 6-coordinate geometry to three equivalent Pr3+, three equivalent Cr+4.50+, and three B2- atoms. There is one shorter (1.77 Å) and two longer (1.80 Å) B–B bond length. In the second B2- site, B2- is bonded in a 9-coordinate geometry to two equivalent Pr3+, four equivalent Cr+4.50+, and three B2- atoms. The B–B bond length is 1.82 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Pr(CoP3)4 by Materials Project

Pr(CoP3)4 crystallizes in the cubic Im-3 space group. The structure is three-dimensional. Pr3+ is bonded to twelve equivalent P1- atoms to form PrP12 cuboctahedra that share faces with eight equivalent CoP6 octahedra. All Pr–P bond lengths are 3.00 Å. Co+2.25+ is bonded to six equivalent P1- atoms to form CoP6 octahedra that share corners with six equivalent CoP6 octahedra and faces with two equivalent PrP12 cuboctahedra. The corner-sharing octahedral tilt angles are 60°. All Co–P bond lengths are 2.26 Å. P1- is bonded in a 2-coordinate geometry to one Pr3+, two equivalent Co+2.25+, and two equivalent P1- atoms. There are one shorter (2.29 Å) and one longer (2.31 Å) P–P bond lengths.

36 MATERIALS SCIENCE↗
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↗