Rare earth-ruthenium-magnesium intermetallics

2017 ◽  
Vol 72 (6) ◽  
pp. 447-455
Author(s):  
Sebastian Stein ◽  
Marcel Kersting ◽  
Lukas Heletta ◽  
Rainer Pöttgen
Keyword(s):  
Rare Earth ◽  
Large Family ◽  
Structural Motif ◽  
X Ray Diffraction ◽  
Space Group ◽  
Cscl Type ◽  
Magnesium Compounds ◽  
Pauli Paramagnetism ◽  
The Common ◽  
Subgroup Scheme

AbstractEight new intermetallic rare earth-ruthenium-magnesium compounds have been synthesized from the elements in sealed niobium ampoules using different annealing sequences in muffle furnaces. The compounds have been characterized by powder and single crystal X-ray diffraction. Sm9.2Ru6Mg17.8 (a=939.6(2), c=1779(1) pm), Gd11Ru6Mg16 (a=951.9(2), c=1756.8(8) pm), and Tb10.5Ru6Mg16.5 (a=942.5(1), c=1758.3(4) pm) crystallize with the tetragonal Nd9.34Ru6Mg17.66 type structure, space group I4/mmm. This structure exhibits a complex condensation pattern of square-prisms and square-antiprisms around the magnesium and ruthenium atoms, respectively. Y2RuMg2 (a=344.0(1), c=2019(1) pm) and Tb2RuMg2 (a=341.43(6), c=2054.2(7) pm) adopt the Er2RuMg2 structure and Tm3Ru2Mg (a=337.72(9), c=1129.8(4) pm) is isotypic with Sc3Ru2Mg. Tm3Ru2Mg2 (a=337.35(9), c=2671(1) pm) and Lu3Ru2Mg2 (a=335.83(5), c=2652.2(5) pm) are the first ternary ordered variants of the Ti3Cu4 type, space group I4/mmm. These five compounds belong to a large family of intermetallics which are completely ordered superstructures of the bcc subcell. The group-subgroup scheme for Lu3Ru2Mg2 is presented. The common structural motif of all three structure types are ruthenium-centered rare earth cubes reminicent of the CsCl type. Magnetic susceptibility measurements of Y2RuMg2 and Lu3Ru2Mg2 samples revealed Pauli paramagnetism of the conduction electrons.

Solid Solutions RE16Rh11–xZx (RE = La, Ce, Pr, Nd, Sm; Z = Ga, Zn, Cd, In, Sn, Sb, Pb, Bi) – Centrosymmetric n = 2 Variants of Parthé’s Homologous Series A5n+6B3n+5

2012 ◽  
Vol 67 (6) ◽  
pp. 594-604 ◽  
Author(s):  
Frank Tappe ◽  
Falko M. Schappacher ◽  
Thorsten Langer ◽  
Inga Schellenberg ◽  
Rainer Pöttgen
Keyword(s):  
Single Crystal ◽  
Solid Solutions ◽  
Homologous Series ◽  
High Frequency ◽  
Structural Motif ◽  
X Ray Diffraction ◽  
Space Group ◽  
X Ray ◽  
Subgroup Scheme ◽  
A Chain

Several samples of solid solutions RE16Rh11-xZx (RE = La, Ce, Pr, Nd, Sm; Z = Ga, Zn, Cd,In, Sn, Sb, Pb, Bi) were synthesized by high-frequency melting of the elements in sealed tantalum ampoules. The samples were characterized by powder X-ray diffraction, and the structures of eight compounds were refined on the basis of single-crystal X-ray diffractometer data. The compounds crystallize with a centrosymmetric variant (space group P4⁄mbm) of the Ca16Sb11 type (P4̄ 21m). The relation between both structure types is discussed on the basis of a group-subgroup scheme. Only for La16Rh8Sn3 we observed full rhodium-tin ordering. The striking structural motif is a chain of face-sharing square prisms (filled with tin) and anti-prisms (filled with rhodium). The La16Rh8Sn3 structure is closely related to the structure types W5Si3, Ca16Sb11, Y3Rh2, Sm26Co11Ga6, Pu31Pt20, and Yb36Sn23 and is the centrosymmetric n = 2 member of Parthé’s A5n+6B3n+5 series. 119Sn Mössbauer spectra resolved the two crystallographically independent tin sites of La16Rh8Sn3, while a Pr16Rh9Sb2 sample shows only a singlet in its 121Sb Mössbauer spectrum.

Intermediate-valent Ce23Ru7Mg4 and RE23Ru7Mg4 (RE = La, Pr, Nd) with Pr23Ir7Mg4-type Structure

2009 ◽  
Vol 64 (11-12) ◽  
pp. 1345-1352 ◽  
Author(s):  
Stefan Linsinger ◽  
Matthias Eul ◽  
Wilfried Hermes ◽  
Rolf-Dieter Hoffmann ◽  
Rainer Pöttgen
Keyword(s):  
Magnetic Susceptibility ◽  
Rare Earth ◽  
Single Crystal ◽  
Magnetic Moment ◽  
Induction Furnace ◽  
Type Structure ◽  
Space Group ◽  
Structure Space ◽  
Magnesium Compounds ◽  
Intermediate Valent

The rare earth-rich magnesium compounds RE23Ru7Mg4 (RE = La, Ce, Pr, Nd) were synthesized from the elements in sealed tantalum ampoules in an induction furnace. They crystallize with the hexagonal non-centrosymmetric Pr23Ir7Mg4-type structure, space group P63mc. The structures of La23Ru6.88(1)Mg4 (a = 1017.7(4), c = 2286.5(5) pm, wR2 = 0.0277, 2708 F2, 71 variables), Ce23Ru7Mg4 (a = 993.5(3), c = 2243.9(8) pm, wR2 = 0.0573, 2268 F2, 70 variables), and Pr23Ru7Mg4 (a = 996.8(3), c = 2241.5(6) pm, wR2 = 0.0492, 2565 F2, 70 variables) have been refined from single-crystal diffractometer data. The structures are built up from complex threedimensional networks of edge- and corner-sharing RE6Ru trigonal prisms. Cavities within these networks are filled by slightly elongated Mg4 tetrahedra (311 - 315 pm in Pr23Ru7Mg4) and RE6 octahedra. The cerium compound has an a parameter which is even smaller than that of Nd23 Ru7Mg4, indicating intermediate-valent cerium. This was confirmed by magnetic susceptibility measurements. Ce23Ru7Mg4 shows an average, reduced magnetic moment of 2.01 μB/Ce atom. Pr23Ru7Mg4 contains stable trivalent praseodymium (3.64 μB/Pr atom)

Structural chemistry of NaCoPO4

1996 ◽  
Vol 52 (3) ◽  
pp. 440-449 ◽  
Author(s):  
R. Hammond ◽  
J. Barbier
Keyword(s):  
High Temperature ◽  
Low Temperature ◽  
Large Family ◽  
X Ray Diffraction ◽  
Tetrahedral Framework ◽  
Space Group ◽  
X Ray ◽  
Cell Parameters ◽  
Tetrahedral Sites ◽  
Bond Valence Analysis

Sodium cobalt phosphate, NaCoPO4, occurs as two different polymorphs which transform reversibly at 998 K. The crystal structures of both polymorphs have been determined by single-crystal X-ray diffraction. The low-temperature form α-NaCoPO4 crystallizes in the space group Pnma with cell parameters: a = 8.871 (3), b = 6.780 (3), c = 5.023 (1) Å, and Z = 4 [wR(F 2) = 0.0653 for all 945 independent reflections]. The α-phase contains octahedrally coordinated Co and Na atoms and tetrahedrally coordinated P atoms, and is isostructural with maracite, NaMnPO4. The structure of high-temperature β-NaCoPO4 is hexagonal with space group P65 and cell parameters: a = 10.166 (1), c = 23.881 (5) Å, and Z = 24 [wR(F 2) = 0.0867 for 4343 unique reflections]. The β-phase belongs to the large family of stuffed tridymites, with the P and Co atoms occupying tetrahedral sites and the Na atoms located in the cavities of the tetrahedral framework. The long c axis corresponds to a 3 × superstructure of the basic tridymite framework (c ≃ 8 Å) and is caused by the displacement of the Na atoms, tetrahedral tilts and strong distortions of the CoO4 tetrahedra. A bond-valence analysis of these phases reveals that the polymorphism in NaCoPO4 is due in part to over-/underbonding of the Na atom in the low-/high-temperature structures, respectively.

Rare Earth-rich Magnesium Compounds RE4RhMg (RE = Y, La–Nd, Sm, Gd–Tm, Lu)

2007 ◽  
Vol 62 (5) ◽  
pp. 642-646 ◽  
Author(s):  
Selcan Tuncel ◽  
Ute Ch. Rodewald ◽  
Bernard Chevalier ◽  
Rainer Pöttgen
Keyword(s):  
Rare Earth ◽  
High Frequency ◽  
Three Dimensional ◽  
Earth Metal ◽  
X Ray Diffraction ◽  
X Ray ◽  
Dimensional Network ◽  
Magnesium Compounds ◽  
Rare Earth Coordination ◽  
Trigonal Prismatic

Abstract The series of magnesium compounds RE4RhMg (RE = Y, La-Nd, Sm, Gd-Tm, Lu) was prepared by high-frequency melting of the elements in sealed tantalum tubes. All samples were investigated by powder X-ray diffraction. The structures with RE = Sm, Gd, Dy, Ho, and Er as rare earth metal components were refined from single crystal diffractometer data: Gd4RhIn-type, F4̄3m, Z = 16, a = 1392.1(1) pm, wR2 = 0.060, 616 F2 values, 19 variables for Sm4RhMg, a = 1380.8(2) pm, wR2 = 0.071, 530 F2 values, 19 variables for Gd4RhMg, a = 1366.9(1) pm, wR2 = 0.070, 594 F2 values, 20 variables for Dy4RhMg, a = 1355.7(2) pm, wR2 = 0.077, 578 F2 values, 20 variables for Ho3.52RhMg1.48, and a = 1355.4(2) pm, wR2 = 0.075, 559 F2 values, 20 variables for Er3.94RhMg1.06 .The rhodium atoms have slightly distorted trigonal prismatic rare earth coordination. Condensation of the RhRE6 prisms leads to a three-dimensional network which leaves large voids that are filled by regular Mg4 tetrahedra with a Mg-Mg distance of 312 pm in Sm4RhMg. The magnesium atoms have twelve nearest neighbors (3 Mg + 9 RE) in icosahedral coordination. In the structures with holmium and erbium, the RE1 positions which are not involved in the trigonal prismatic network exhibit RE1/Mg mixing. Shortest distances occur for Sm-Rh (286 pm) within the rigid three-dimensional network of condensed trigonal prisms.

Condensed [Ru4Sn6] Units in the Stannides LnRu4Sn6 (Ln = La, Pr, Nd, Sm, Gd) - Synthesis, Structure, and Chemical Bonding

1999 ◽  
Vol 54 (7) ◽  
pp. 863-869 ◽  
Author(s):  
Markus F. Zumdick ◽  
Rainer Pöttgen
Keyword(s):  
Rare Earth ◽  
Single Crystals ◽  
Chemical Bonding ◽  
Melting Furnace ◽  
Structural Motif ◽  
X Ray Diffraction ◽  
X Ray ◽  
Arc Melting ◽  
First Time ◽  
Gadolinium Compound

The stannides LnRu4Sn6 (Ln = La, Pr, Nd, Sm, Gd) were prepared by reaction of the elements in an arc-melting furnace and subsequent annealing at 1120 K. The praseodymium, the neodymium, and the samarium stannide were obtained for the first time. The LnRu4Sn6 stannides were investigated by X-ray diffraction both on powders and single crystals. They adopt the YRu4Sn6 type structure which was refined from single crystal X-ray data for the samarium and the gadolinium compound: I4̄2m, a = 686.1 (1), c = 977.7(2) pm, wR2 = 0.0649, 483 F2 values for SmRu4Sn6, and a = 685.2(1), c = 977.6(3) pm, wR2 = 0.0629, 554 F2 values for GdRu4Sn6 with 19 variables for each refinement. The striking structural motif of these stannides are distorted RuSn6 octahedra with Ru-Sn distances ranging from 257 to 278 pm. Four of such octahedra are condensed via common edges and faces forming [Ru4Sn6] units which are packed in a tetragonal body-centered arrangement. The rare-earth atoms fill the voids between the [Ru4Sn6] units. Based on an extended Hückel calculation, strong bonding interactions were found for the Ru-Sn and the various Sn-Sn contacts.

Neue ternäre Phasen in den Systemen Seltene Erden-Lithium-Zinn

1993 ◽  
Vol 208 (1) ◽  
Author(s):  
A. Allescher-Last ◽  
A. Czybulka ◽  
H.-U. Schuster
Keyword(s):  
Rare Earth ◽  
X Ray Diffraction ◽  
Space Group ◽  
X Ray ◽  
Ternary Compounds ◽  
Seltene Erden

AbstractNew ternary compounds in the systems Rare Earth-Lithium-Tin have been prepared and characterized by X-ray diffraction. They crystallize in two different structure types. The equiatomic compounds with RE = Ce-Sm, Gd-Tm and Lu are isotypic to YLiSn crystallizing hexagonally in space group

Rows of corner- and face-sharing Mg4 tetrahedra arranged as hexagonal rod packing in the hexagonal Laves phases REMg2 and the rare earth-rich phases RE9CoMg4 (RE=Y, Dy-Tm, Lu)

2018 ◽  
Vol 233 (9-10) ◽  
pp. 607-613 ◽  
Author(s):  
Sebastian Stein ◽  
Rainer Pöttgen
Keyword(s):  
Rare Earth ◽  
Rare Earth Metal ◽  
Diffraction Data ◽  
Earth Metal ◽  
Structural Motif ◽  
Induction Melting ◽  
X Ray Diffraction ◽  
Laves Phases ◽  
X Ray ◽  
The Many

Abstract Six new rare earth metal-rich intermetallic compounds RE9CoMg4 with RE=Y, Dy, Ho, Er, Tm and Lu were synthesized by induction-melting the elements in sealed niobium ampoules followed by annealing in muffle furnaces. The structures of Y9CoMg4 and Tm8.56CoMg4.44 were refined from single-crystal X-ray diffraction data: P63/mmc, a=965.65(6), c=971.07(5) pm, wR2=0.0599, 614 F2 values, 20 variables for Y9CoMg4 and a=945.20(4), c=953.11(5) pm, wR2=0.0358, 585 F2 values, 21 variables for Tm8.56CoMg4.44 (a small homogeneity range results from Tm/Mg mixing). The RE9CoMg4 phases crystallize with a coloring variant of the aristotype Co2Al5. The striking structural motif is a hexagonal rod packing of rows of corner- and face-sharing tetrahedral Mg4 clusters with Mg–Mg distances ranging from 304 to 317 pm in Y9CoMg4. These rows are similar to the hexagonal Laves phases REMg2. The space between the rows is filled with rows of face-sharing Co@Y6 trigonal prisms (TP) and empty Y6 octahedra (O) in the sequence –TP–O–O–. The many isopointal coloring variants of the aristotype Co2Al5 are briefly discussed.

Crystal structures of rare earth elements rich apatite analogues

1990 ◽  
Vol 191 (3-4) ◽  
Author(s):  
Nicoline Kalsbeek ◽  
Sine Larsen ◽  
Jørn G. Rønsbo
Keyword(s):  
Rare Earth ◽  
Rare Earth Elements ◽  
Crystal Structures ◽  
X Ray Diffraction ◽  
Hexagonal System ◽  
Space Group ◽  
X Ray ◽  
Cell Dimensions

AbstractThe crystal structures have been determined for britholite-(Ce) and lessingite-(Ce) from the type localities and a third sample (‘min X’) showing chemical similarities to both britholite-(Ce) and lessingite-(Ce). This sample is from the Ilímaussaq intrusion in Greenland. They are rare earth elements (REE) rich apatite analogues. Based on the X-ray diffraction results they were assigned to the hexagonal system with cell dimensions slightly larger than those of apatite. The three structures have been refined in the space group

Ternary rhombohedral Laves phases RE2Rh3Ga (RE = Y, La–Nd, Sm, Gd–Er)

2017 ◽  
Vol 72 (4) ◽  
pp. 289-303 ◽  
Author(s):  
Stefan Seidel ◽  
Oliver Janka ◽  
Christopher Benndorf ◽  
Bernhard Mausolf ◽  
Frank Haarmann ◽  
...  
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Susceptibility ◽  
Rare Earth ◽  
Low Temperatures ◽  
Nmr Spectra ◽  
X Ray Diffraction ◽  
Laves Phases ◽  
X Ray ◽  
Arc Melting ◽  
Pauli Paramagnetism

Abstract:The ordered Laves phases RE2Rh3Ga (RE=Y, La–Nd, Sm, Gd–Er) were synthesized by arc-melting of the elements and subsequent annealing. The samples were characterized by powder X-ray diffraction (XRD). They crystallize with the rhombohedral Mg2Ni3Si type structure, space group R3̅m. Three structures were refined from single crystal X-ray diffractometer data: a=557.1(1), c=1183.1(2), wR2=0.0591, 159 F2 values, 10 variables for Y2Rh3Ga, a=562.5(2), c=1194.4(2) pm, wR2=0.0519, 206 F2 values, 11 variables for Ce2Rh3Ga and a=556.7(2), c=1184.1(3) pm, wR2=0.0396, 176 F2 values, 11 variables for Tb2Rh3Ga. The Rh3Ga tetrahedra are condensed via common corners and the large cavities left by the network are filled by the rare earth atoms. The RE2Rh3Ga Laves phases crystallize with a translationengleiche subgroup of the cubic RERh2 Laves phases with MgCu2 type. Magnetic susceptibility measurements reveal Pauli paramagnetism for Y2Rh3Ga and La2Rh3Ga. Ce2Rh3Ga shows intermediate cerium valence while all other RE2Rh3Ga phases are Curie–Weiss paramagnets which order magnetically at low temperatures. The 89Y and 71Ga solid state nuclear magnetic resonance (NMR) spectra of the diamagnetic representative Y2Rh3Ga show well-defined single resonances in agreement with an ordered bulk phase. In comparison to the binary Laves phase YRh2 a strongly increased 89Y resonance frequency is observed owing to a higher s-electron spin density at the 89Y nuclei as proven by density of states (DOS) calculations.

scholarly journals Equiatomic iron-based tetrelides TFeSi and TFeGe (T = Zr, Nb, Hf, Ta) – A 57Fe Mössbauer-spectroscopic study

2019 ◽  
Vol 74 (2) ◽  
pp. 211-219 ◽  
Author(s):  
Sebastian Stein ◽  
Theresa Block ◽  
Steffen Klenner ◽  
Lukas Heletta ◽  
Rainer Pöttgen
Keyword(s):  
Room Temperature ◽  
Structural Motif ◽  
Clear Correlation ◽  
X Ray Diffraction ◽  
X Ray ◽  
Arc Melting ◽  
Structural Distortions ◽  
Trigonal Prismatic Coordination ◽  
The Common ◽  
Trigonal Prismatic

AbstractThe equiatomic iron-silicides TFeSi as well as the corresponding germanides TFeGe with the electron-poor 4d and 5d transition metals (T=Zr, Nb, Hf, Ta) have been synthesized from the elements by arc-melting. All samples were characterized through their lattice parameters using powder X-ray diffraction (Guinier technique). Four structures were refined from single-crystal X-ray diffractometer data: a=640.16(3), b=393.45(5), c=718.42(6) pm, Pnma, 390 F2 values, 20 parameters, wR2=0.0294 for ZrFeSi (TiNiSi type), a=719.63(11), b=1119.27(7), c=649.29(7) pm, Ima2, 1103 F2 values, 54 parameters, wR2=0.0555 for NbFeGe (TiFeSi type), a=655.96(7), c=372.54(4) pm, P6̅2m, 251 F2 values, 15 parameters, wR2=0.0260 for HfFeGe (ZrNiAl type) and a=624.10(3), b=378.10(6), c=725.25(7) pm, Pnma, 369 F2 values, 20 parameters, wR2=0.0513 for TaFeGe (TiNiSi type). The common structural motif of the four different structures is the slightly distorted tetrahedral tetrel (tr) coordination of the iron atoms and a trigonal prismatic coordination of iron by T=Zr, Nb, Hf, Ta. Three compounds were characterized as Pauli-paramagnetic by measuring their susceptibility. The measurement of the electrical resistivity of NbFeSi characterises this compound as a good metal. Furthermore, 57Fe Mössbauer spectra of all compounds could be obtained at room temperature, revealing a clear correlation between the structural distortions and the quadrupole splitting parameters.

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