Small Homogeneity Range Research Articles

Cadmium-Auride AIICdxAu2– x (AII = Ca, Sr) Synthese, Kristallstruktur, chemische Bindung/ Cadmium-Aurides AIICdxAu2−x (AII = Ca, Sr) – Synthesis, Crystal Structure, Chemical Bonding

Following the observation that the binary dicadmides and diaurides of calcium and strontium (A) both form the KHg2 structure type, the two sections AIICdxAu2−x have been studied systematically by means of synthetic, X-ray structural and theoretical investigations. The binary border compound CaCd2 is dimorphic forming the KHg2 structure at elevated temperatures (orthorhombic, space group Imma, a = 488.63(9), b = 754.1(2), c = 851.3(2) pm, Z = 4, R1 = 0.0498) and the MgZn2-type Laves phase at ambient conditions (hexagonal, space group P63/mmc, a = 599.71(9), c = 962.7(2) pm, Z = 4, R1 = 0.0309). Starting from the known binary calcium auride CaAu2 only a very small amount of Au can be replaced by Cd. Around the 1 : 1 ratio of Au and Cd the TiNiSi structure type (orthorhombic, space group Pnma), an ordered variant of the KHg2 type, has a small homogeneity range (CaCdxAu2−x with x = 1/0.76(2): a = 735.0(1)/731.7(1), b = 433.66(6)/431.43(7), c = 873.7(2)/869.9(2) pm, Z = 4, R1 = 0.0482/0.0539). The analogous structure type is also observed in the Sr compounds with the difference that in this case a continuous transition from the KHg2 type of SrAu2 (i. e. x = 0) towards the distorted TiNiSi structure type (up to x = 0.86) is observed in the series SrCdxAu2−x (for x = 0.86(1)/0.45(1): a = 764.0(1)/758.4(1), b = 458.07(7)/474.6(1), c = 872.16(12)/829.2(2) pm, Z = 4, R1 = 0.0446/0.0410). Attempts to prepare the Ca compounds of intermediate composition around a Cd content of x ≈ 0.5 resulted in the formation of the Aurich phase Ca5Cd2Au10 crystallizing with the Zr7Ni10 structure type (orthorhombic, space group Cmca, a = 1390.6(4), b = 1015.7(3), c = 1025.6(2) pm, Z = 4, R1 = 0.0657). In this compound, Cd and Ca occupy common crystallographic sites, which are occupied by In in the isotypic ternary compound Ca4In3Au10. Similarly, at the Cd-rich parts of the sections AIICdxAu2−x no simple phase width of the KHg2 structure type exists. In the case of the calcium series the new compound Ca11Cd18Au4, which shows only a very small phase width, is formed instead. This compound crystallizes with a new structure type (Ca11Cd18+xAu4−x with x = 0.6/0: tetragonal, space group I41/amd, a = 1030.83(6)/1029.39(6), c = 3062.5(3)/3051.0(3) pm, Z = 4, R1 = 0.0475/0.0379) exhibiting a complicated Cd/Au polyanion with four-, five- and six-bonded Cd/Au atoms. The results of FPLAPWband structure calculations are used to explain the electronic stability of the compounds. The calculated Bader charges of cadmium and gold atoms (and In and Au atoms for comparison) are used to discuss the transition between Cd-rich cadmides (like CaCd2 and Ca11Cd18Au4), auridocadmates (like CaCdAu) and the Cd-poor cadmium aurides (like Ca5Cd2Au10).

Isothermal section of the Dy–Co–Ti ternary system at 500 °C

The isothermal section of the Dy–Co–Ti system at 500 °C has been investigated in the whole composition range by means of X-ray diffraction, thermal analysis, scanning electron microscopy and energy dispersive X-ray spectroscopy. The only ternary phase DyTi x Co 12− x is of ThMn 12-type structure, space group I4/ mmm, and shows a small homogeneity range of 1 ≤ x ≤ 1.6. The lattice parameters for DyTi x Co 12− x with 1 ≤ x ≤ 1.56 are a = 0.8336(4)–0.8402(1) nm and c = 0.4691(3)–0.4727(1) nm. Along a constant Dy concentration, the solid solubilities of Ti in the compounds Dy 2Co 17, DyCo 3, DyCo 2 and Dy 3Co are about 2.0, 2.0, 3.0 and 4.0 at.%, respectively. The TiCo phase has a homogeneity range of 50–54 at.% Co at 500 °C and dissolves up to 2.0 at.% Dy.

Crystal Structure Of Magnesium Iridoboride, MglrB

BIrMg, hexagonal, P6222 (no. 180), a = 5.2752(7) A, c = 9.439(2) A, V = 227.5 A, Z = 6, Rgt(F) = 0.017, wRref(F) = 0.019, T = 295 K. Source of material The MgIrB compound was prepared using powders of Mg (99.8 %), Ir (99.9%) and crystalline B (99.999%) as startingmaterials. The elements mixture was ground, pressed into pellets, embedded in Ta ampoules and sealed under argon. The annealing was performed at 1293 K for 14 days and at 1333 K for 15 days with intermediate re-grinding. Experimental details The single phase samplewas obtained from the samplewith nominal composition Mg1.1IrB1.1. The X-ray powder diffraction patternwas indexedwith a hexagonal unit cell and lattice parameters a = 5.2736(3)A and c = 9.4358(7)A.When changing initial mixture compostition to Mg0.96IrB0.94 a slight lattice parameters reduction to a = 5.2702(2) A, c = 9.429(1) A was observed. The largest lattice parameters (cf. Abstract) were found for theMgIrB single crystal obtained from the sample with nominal composition Mg1.38IrB1.46 by annealing at 1273 K for 18 days. Analogously to the Mg RhB 1.x phase [1] we assume a small homogeneity range for Mg IrB 1.x with the minimum x close to 0 observed in the single crystal used for the structure determination. The Flack parameter value of 0.0 reveals correctness of the absolute structure. Discussion The synthesis of numerous ternary magnesium rhodium borides [1-4] initiated us to study the Mg-Ir-B system with iridium as the electron analogue of rhodiumwith the aim to investigate the platinummetal nature influence on the crystal structure and chemical bonding of ternary borides. The crystal structure of MgIrB is similar to Mg RhB 1.x [1]. It can be described as a framework of the distorted trigonal prisms [BIr4(Mg2)2], sharing the bases and side edges. The distorted hexagonal channels of the framework directed along c axis are occupied by Mg1 atoms. Each boron atom forms a short distance of 1.87(1) A to the next boron atom and, in addition, short distances of 2.203(3) and 2.210(7)A to the next iridium atoms. On this way a 2D [IrB] network is formed. In Mg RhB 1.x [1] the 2D [RhB] network was shown to be anionic. In analogy, we suppose the same character for 2D [IrB]. For theMg RhB 1.x compound the vacancies inMg1 site were experimentally observed and then interpreted using the results of chemical bonding analysis. The single crystal diffraction data for theMgIrB show the full occupation of theMg1 positions (99.8(2) %) and yield the composition MgIrB (x = 0). It agrees with the maximum lattice parameters found for the single crystal data. Z. Kristallogr. NCS 224 (2009) 17-18 / DOI 10.1524/ncrs.2009.0010 17 © by Oldenbourg Wissenschaftsverlag, Munchen Crystal: black prism, size 0.050 × 0.020 × 0.020 mm Wavelength: Mo K0 radiation (0.7107 A) %: 930.5 cm Diffractometer, scan mode: Rigaku AFC7, )/2 2max: 63.01° N(hkl)measured, N(hkl)unique: 2830, 244 Criterion for Iobs, N(hkl)gt: Iobs > 2 !(Iobs), 227 N(param)refined: 15 Programs: WinCSD [5], ATOMS [6], SHELXS-97 [7] Table 1. Data collection and handling. B 6j 0.602(2) 2x$1 1⁄2 0.006(2) Table 2. Atomic coordinates and displacement parameters (in A). Atom Site x y z Uiso

The crystal structure of Hf 1.5+δNb 1.5−δAs and structure–composition relations in the section Hf 3As–Nb 3As

The title compound Hf 1.5+ δ Nb 1.5− δ As was characterized by means of single crystal X-ray diffraction. It represents a new structure type of intermetallic compounds (space group Pnma; lattice parameters a=7.142(2) Å, b=3.583(2) Å, c=11.640(2) Å) and shows a small homogeneity range corresponding to (0.1< δ<0.25) at 1400 °C. The crystal structure may be visualized by a combination of As-centred trigonal prisms of the metal atoms and bcc-like fragments formed by metal atoms. Structural relations with various binary arsenides are discussed. The structure of Hf 1.5+ δ Nb 1.5− δ As shows significant preferred site occupation of Hf and Nb at the three independent metal positions (differential fractional site occupancy). Structure–composition relations in the section Hf 3As–Nb 3As which also contains the new phase Hf 2+ δ Nb 1− δ As with Ti 3P-type structure (space group P4 2/ n) are discussed. Ground state energies of various ordered compounds with Hf 1.5+ δ Nb 1.5− δ As-, Ti 3P- and Ta 3As-type structures were calculated from ab initio density functional theory. These energies were used for thermodynamic calculations employing the compound energy formalism (CEF) with the aim to model the experimentally observed site fraction data for both ternary compounds as well as Gibbs energies at the temperature of equilibration (1400 °C).

Experimental reinvestigation of the Co–Nb phase diagram

The phase diagram of the binary Co–Nb system was redetermined in the whole range of compositions by differential thermal analysis (DTA), electron-probe micro analysis (EPMA), powder X-ray diffraction (XRD), and metallography. Equilibrated alloys of more than 30 different compositions and a series of diffusion couples were used in order to establish the invariant reactions in the system and the homogeneity ranges of all phases. A special feature of the Co–Nb system is the occurrence of three different types of the Laves phase NbCo 2, which are a cubic variant (C15) and two different hexagonal variants (C14 and C36). The existence of these three types of the Laves phase was confirmed and their homogeneity ranges were established for the first time. The two hexagonal Laves phase variants are stable only at high temperatures and strongly off-stoichiometric compositions. Two more intermetallic compounds exist in the system: The monoclinic phase Nb 2Co 7 forms by a peritectoid reaction and has a very small homogeneity range, whereas the μ phase Nb 6Co 7 in the central part of the system melts congruently and is stable within a broad homogeneity range.

Alkaline-Earth Metal Mercury Intermetallics A11−xHg54+x (A = Ca, Sr)

Re-examination of the mercury-rich regions of the Ca-Hg and Sr-Hg phase diagrams has shown that the phases previously identified as "AHg 3.6" should be reformulated as A(11-x) Hg(54+x) (A = Ca, Sr). The crystal structures for representative members of these A 11- x Hg 54+ x phases were determined from single-crystal X-ray diffraction data (Pearson symbol hP65, space group P6; a = 13.389(1) A, c = 9.615(1) A for Ca(10.92(2))Hg(54.08) (x = 0.08(2)); a = 13.602(2) A, c = 9.818(1) A for Sr(10.48(4))Hg(54.52) ( x = 0.52(4))) and confirmed by powder Rietveld refinements ( R B = 0.020 for Ca(10.7(2))Hg(54.3) and 0.014 for Sr(10.7(3))Hg(54.3)). Diverse coordination polyhedra surround the A (CN14-16, multiply capped pentagonal or hexagonal prisms as well as Friauf polyhedra) and Hg atoms (CN11-13, pentacapped trigonal prisms and icosahedra). Partial disorder of Hg into one of the A sites accounts for the nonstoichiometry in the A(11-x)Hg(54+ x) phases. If this disordered A site is completely occupied by Hg atoms, the composition is constrained to a maximum of x = 2 in A(11-x)Hg(54+ x), corresponding to a small homogeneity range of "A(0.14-0.17)Hg(0.86-0.83)"; the true homogeneity range is likely narrower. The structure can be regarded as being built up from a stacking of triangular nets with hexagonal voids that are filled with single atoms or various clusters. In particular, the presence of triangular Hg 3 clusters in ordered orientations distinguishes this structure from that of the related Gd 14Ag 51-type structure, in which triangular Ag 3 clusters are in disordered orientations. Band structure calculations reveal a small degree of electron transfer from the A to Hg atoms, supporting the presence of a partially anionic mercuride substructure.

Synthesis, Structure and Chemical Bonding of RE4RuMg (RE = La–Nd, Sm, Gd–Ho)

AbstractThe rare earth metal rich compounds RE4RuMg (RE = La–Nd, Sm, Gd–Ho) were obtained by induction‐melting of the elements in sealed tantalum tubes in a water‐cooled sample chamber of a high‐frequency furnace. The RE4RuMg compounds were studied by powder X‐ray diffraction: Gd4RhIn type, $F {\rm {\bar 4}}{\rm 3}m$, a = 1433.6(2) pm for La4RuMg, a = 1408.1(2) pm for Ce4RuMg, a = 1405.9(1) pm for Pr4RuMg, a = 1399.5(3) pm for Nd4RuMg, a = 1384.7(1) pm for Sm4RuMg, a = 1381.4(2) pm for Gd4RuMg, a = 1371.1(2) pm for Tb4RuMg, a = 1367.2(2) pm for Dy4RuMg, and a = 1361.4(5) pm for Ho4RuMg. The structures of RE4RuMg with RE = La, Pr, Nd, and Sm were refined from single crystal diffractometer data. The RE4RuMg structures consist of a three‐dimensional network of edge‐ and corner‐sharing RuRE6 trigonal prisms. In contrast to the isotypic series RE4CoMg and RE4RhMg, the ruthenium atoms displace from the centers of the prisms. The voids within the three‐dimensional network are filled by regular Mg4 tetrahedra at a Mg–Mg distance of 316 pm in La4RuMg. The magnesium atoms have icosahedral coordination by three magnesium and nine rare earth metal atoms. The samarium based crystal revealed a small homogeneity range Sm3−xRu1+yMg1+x−y leading to the refined composition Sm3.92Ru1.16Mg0.92. Chemical bonding in La4RuMg was studied in comparison with La4CoMg. The La1–Mg bonding is found to be dominating among the La–Mg interactions in both systems. Differences in chemical bonding due to a reduced valence electron concentration and different La2–Ru versus La3–Ru distances within RuLa23La33 prisms are traced out.

Crystal structure and local order in Co6Al11−x Si6+x

The ternary compound Co(6)Al(11-x)Si(6+x) (epsilon phase) was prepared from the elements by arc melting and subsequent heat treatment, and then characterized by single-crystal X-ray diffraction (XRD), electron-probe microanalysis (EPMA), differential thermal analysis (DTA) and transmission electron microscopy (TEM). This new structure type consists of planar layers with the composition [Co(6)Al(10)Si(4)], which are penetrated by perpendicular (Si-Si-Al) chains. While the layers are well described by an orthorhombic model (space group Pnma, Pearson symbol oP46), the chains exhibit doubled periodicity, thus yielding a superstructure. Two alternative ordering models (space group Cmc2(1), oC184, and space group P2(1)/c, mP92) are presented and discussed based on XRD and TEM results. The (Si-Si-Al) chains are located in pentagonal antiprismatic ;channels' which reveal the similarity of the Co(6)Al(11-x)Si(6+x) structure to Al-rich transition-metal compounds such as Co(4)Al(13), Co(2)Al(5), Fe(4)Al(13), V(7)Al(45), V(4)Al(23) and VAl(10), which also exhibit this type of pentagonal ;channels' in their crystal structures. The phase shows only a very small homogeneity range.

Chemical Bonding in TiSb2 and VSb2: A Quantum Chemical and Experimental Study

The chemical bonding in the isostructural intermetallic compounds TiSb2 and VSb2, crystallizing in the CuAl2 type, was investigated by means of quantum chemical calculations, particularly the electron localization function (ELF), as well as by Raman spectroscopy, Hall effect and conductivity measurements on oriented single crystals, and high-pressure X-ray powder diffraction. The homogeneity ranges of the compounds were determined by powder X-ray diffraction, WDXS, and DSC measurements. TiSb2 exhibits no significant homogeneity range, while VSb2 shows a small homogeneity range of approximately 0.3 at. %. According to the ELF calculations, the Sb atoms form dumbbells via a two-center two-electron bond, while the T atoms (T = Ti, V) build up chains along the crystallographic c-axis. Both building units are connected by covalent T-Sb-T three-center bonds, thus forming a three-dimensional network. The strength of the bonds involving Sb was determined by fitting a force constant model to the vibrational mode frequencies observed by polarized Raman measurements on oriented single crystals. The resulting bond order of the Sb2 dumbbells is 1, while the strength of the three-center bonds resembles a bond order of 1.5. The weak pressure dependence of the c/a ratio confirms the slightly different bonding picture in TiSb2 compared to that in CuAl2. Electrical transport measurements show the presence of free charge carriers, as well as a metal-like temperature dependence of the electrical resistivity.

A New Preparative Approach to HgPbP14 Structure Type Materials: Crystal Structure of Cu0.73(1)Sn1.27(1)P14 and Characterization of M1−xSn1+xP14 (M = Cu, Ag) and AgSbP14

AbstractA new preparative approach, using main group iodides as mineralization agents, was developed to prepare bulk quantities of HgPbP14 [(M1)(M2)P14] type polyphosphides containing group 11 cations on the M1 and main group elements Sn or formerly unseen Sb on the M2 position. The known (M1)2+:(M2)2+ combination of cations is extended with the combination (M1)1+:(M2)3+ in AgSbP14. A single crystal structure determination was performed for Cu1−xSn1+xP14. Cu0.73(1)Sn1.27(1)P14 crystallizes orthorhombically, space group Pnma (No. 62) with lattice constants a = 12.513(2) Å, b = 9.800(1) Å, c = 10.445(1) Å, V = 1280.8(3) Å3 and Z = 4. Small differences in the cell parameters between the single crystal and powder diffraction experiments of CuSnP14 are probably due to a small homogeneity range. Tetravalent tin postulated beside divalent tin for isostructural Au0.64Sn1.36P14 could not be detected by 119Sn‐Mössbauer spectroscopic experiments for the copper tin polyphosphide.An ionic description like [(M1+)1−x(M24+)x]2+ [(M22+)(P0)10(P1−)4]2− with x = 0.33 according to a Zintl‐Klemm concept has to be substituted by a more covalent description of [(M1+)1−x(M22+)x](1+x)+[(M22+)(P14)](1+x)− for the copper tin polyphosphide.

Syntheses and Crystal Structure of the Ternary Silicides RE2Si2Mg (RE = Y, La–Nd, Sm, Gd–Lu) and Structure Refinement of Dy5Si3

The rare earth metal–magnesium–silicides RE2Si2Mg (RE = Y, La–Nd, Sm, Gd–Lu) were prepared by induction melting of the elements in sealed tantalum tubes in a water-cooled sample chamber of a high-frequency furnace. The silicides were investigated via X-ray powder diffraction. The structures of Sm2Si2Mg and Dy2Si2Mg were refined from X-ray single crystal diffractometer data: Mo2FeB2 type, P4/mbm, a = 727.86(7), c = 428.16(6) pm, wR2 = 0.0194, 206 F2 values, 13 variable parameters for Sm2Si2Mg and a = 713.85(7), c = 419.07(6) pm, wR2 = 0.0331, 286 F2 values, 12 variable parameters for Dy2Si2Mg. The samarium compound shows a small homogeneity range Sm2+xSi2Mg1−x. The investigated single crystal had the refined composition Sm2.022(3)Si2Mg0.978(3). The RE2Si2Mg silicides are 1:1 intergrowth structures of CsCl and AlB2 related slabs of compositions REMg and RESi2. Crystals of the binary silicide Dy5Si3 were obtained as side product. The structure was refined from X-ray single crystal data: Mn5Si3 type, P63/mcm, a = 841.0(2), c = 631.3(1) pm, wR2 = 0.0661, 269 F2 values, 12 variable parameters.

Formation of Multiple Phases with the CaCu5‐Type Structure in the U—Ni—Al Ternary System.

AbstractFor Abstract see ChemInform Abstract in Full Text.

Spin-glass like behavior in a new ternary uranium cobalt aluminide, U3Co4+xAl12$minus;x with x=0.55(2)

The new compound U3Co4+xAl12−x, where x=0.55(2), was prepared by arc-melting of the elemental components, followed by a prolonged annealing at elevated temperature. Scanning electron microscopy-energy-dispersive spectroscopy and powder X-ray diffraction were used to determine the deviation from the ideal stoichiometry. A small homogeneity range, that extends around the composition U3Co4+xAl12−x with 0.4(1) ⩽x⩽0.7(1), could be detected. Single-crystal diffraction experiments revealed that U3Co4.55Al11.45 crystallizes with the Gd3Ru4Al12 type-structure, (space group P63/mmc, Z=2) in a cell of dimensions at room temperature, a=8.6518(2) Å, c=9.2620(2) Å. The crystal structure can be viewed as an intergrowth of two distinct layers of Co and Al atoms, and U, Al and mixed Al/Co atoms that pile up along the hexagonal axis. The results of the DC magnetization suggest the occurrence of a spin glass state at low temperature (Tf=8 K). The origin of freezing of the magnetic moments may arise from a topological frustration due to the location of the U atoms on the apexes of a distorted Kagomé lattice.

Spin-glass like behavior in a new ternary uranium cobalt aluminide, U 3Co 4+ xAl 12− x with x=0.55(2)

The new compound U 3Co 4+ x Al 12− x , where x=0.55(2), was prepared by arc-melting of the elemental components, followed by a prolonged annealing at elevated temperature. Scanning electron microscopy-energy-dispersive spectroscopy and powder X-ray diffraction were used to determine the deviation from the ideal stoichiometry. A small homogeneity range, that extends around the composition U 3Co 4+ x Al 12− x with 0.4(1) ⩽ x⩽0.7(1), could be detected. Single-crystal diffraction experiments revealed that U 3Co 4.55Al 11.45 crystallizes with the Gd 3Ru 4Al 12 type-structure, (space group P6 3/ mmc, Z=2) in a cell of dimensions at room temperature, a=8.6518(2) Å, c=9.2620(2) Å. The crystal structure can be viewed as an intergrowth of two distinct layers of Co and Al atoms, and U, Al and mixed Al/Co atoms that pile up along the hexagonal axis. The results of the DC magnetization suggest the occurrence of a spin glass state at low temperature ( T f=8 K). The origin of freezing of the magnetic moments may arise from a topological frustration due to the location of the U atoms on the apexes of a distorted Kagomé lattice.

LaPdIn2 with MgCuAl2 and REPdIn2 (RE = Y, Pr, Nd, Sm, Gd−Tm, Lu) with HfNiGa2-Type Structure: Synthesis, Structure, and Physical Properties

New indides REPdIn 2 (RE = Y, La, Pr, Nd, Sm, Gd-Tm, Lu) have been synthesized from the elements by arc-melting. The indides with Y, Pr, Nd, Sm, Gd-Tm, and Lu as the rare earth metal component have been obtained in pure form by annealing the arc-melted samples in tantalum containers. Single crystals of LaPdIn 2 were obtained by recrystallization of a LaPdIn 2 sample from an indium flux. LaPdIn 2 crystallizes with the MgCuAl 2 structure: Cmcm, a = 463.79(7) pm, b = 1074.3(2) pm, c = 746.4(2) pm, wR2 = 0.1149, 380 F2 values, and 16 variables. The structure may be described as a palladium-filled LaIn 2 substructure. The latter is a strongly distorted CaIn 2 -like arrangement. Together, the palladium and indium atoms build a three-dimensional [PdIn 2 ] network in which the lanthanum atoms fill distorted pentagonal channels. The other REPdIn 2 indides crystallize with the HfNiGa 2 type, space group I4mm. Single crystals have been obtained for three compounds: a = 1397.7(1) pm, c = 925.5(1) pm, wR2 = 0.0662, 2098 F2 values, 64 variables for PrPdIn 2 ; a = 1368.5(1) pm, c = 912.8(1) pm, wR2 = 0.1113, 2102 F2 values, 65 variables for Tb 0.980(4) PdIn 2.020(4) ; and a = 1358.8(1) pm, c = 908.4(1) pm, wR2 = 0.0777, 1983 F2 values, 64 variables for Tm 0.986(2) PdIn 2.014(2) . The terbium and thulium compounds show a small homogeneity range where the Tb3/Tm3 position shows mixed occupancy with indium. Again, the palladium and indium atoms form a three-dimensional [PdIn 2 ] network, but is more complex when compared with that of LaPdIn 2 . The four crystallographically different rare earth metal atoms lie in larger voids formed by this network. The magnetic and electrical transport properties of REPdIn 2 (RE = Pr, Nd, Sm, Gd, Er, Tm, and Lu) have been studied over wide ranges of temperature and magnetic field. All these indides except for LuPdIn 2 show localized magnetism due to the presence of magnetic moments on the RE 3+ ions. The compounds with RE = Pr, Nd, Sm, and Gd order magnetically at low temperatures. PrPdIn 2 is antiferromagnetic below T N = 5.5 K. The other three phases show complex magnetic behavior below T N = 4.9, 9, and 10 K, for NdPdIn 2 , SmPdIn 2 , and GdPdIn 2 , respectively. In the case of GdPdIn 2 the magnetic ordering involves a strong ferromagnetic component. For SmPdIn 2 another phase transition at T t = 5.5 K has been established, probably a change in the magnetic structure. In contrast to the other compounds, ErPdIn 2 and TmPdIn 2 remain Curie-Weiss paramagnetic down to 1.7 K, and LuPdIn 2 is a Pauli paramagnet. All the compounds studied show metallic conductivity with some features characteristic of crystal field interactions and/or spin fluctuations. The magnetic phase transitions in PrPdIn 2 , NdPdIn 2 , SmPdIn 2 , and GdPdIn 2 manifest themselves as distinct anomalies in the temperature-dependent resistivity. In the ordered state the resistivity shows a behavior reflecting reduction in the spin-disorder scattering.

Formation of multiple phases with the CaCu5-type structure in the U–Ni–Al ternary system

From a systematic study of phase relations in the U–Ni–Al ternary system, we have shown that four independent phases are formed with the hexagonal CaCu5 type: the previously known UNi2Al3, which exhibits a small homogeneity range UNi2+xAl3−x (0<x<0.15), two new phases, UNi2+yAl3−y (0.9<y<1) and UNi4.55Al0.45, and a ternary extension UNi4−zAlz (0<z<0.5) of the binary UNi4. Crystal structure refinements of single crystals of the new compositions UNi2.9Al2.1 (a=5.0108Å, c=4.1093Å) and UNi4.55Al0.45 (a=4.8032Å, c=4.04173Å) indicate that the Ni/Al substitution occurs on the 3g Wyckoff site only. The new phases are paramagnetic down to liquid helium temperature.

Effect of rare earth content on microstructure and magnetic properties of SmCo and NdFeB thin films

Thin films of highly anisotropic rare earth intermetallic compounds increasingly come into the focus of interest for application in magnetic miniature devices. We prepared hard magnetic SmCo and NdFeB films by pulsed laser deposition and investigated the influence of rare-earth content on phase formation, microstructure, and magnetic properties. The phase evolution with rare earth content, as observed by x-ray diffraction, shows a distinct difference for the two systems. For SmCo a disordered SmCo7 structure is found at low Sm content and a change in the lattice constants is observed for a Sm-rich sample. Simultaneously, the coercive field improves whereas the magnetic in-plane texture found for Sm-poor films vanishes for higher Sm content. For NdFeB the increase in Nd content leads to an additional Nd phase because of the small homogeneity range. Contrary to the bulk, coercivity is reduced, which can be attributed to a significant increase of grain size and roughness.

Structural Chemistry of the Neptunium–Germanium Binary System

The structural chemistry of the complete binary neptunium–germanide system has been investigated by means of X-ray diffraction. In addition to the well-known NpGe3 (AuCu3 type), at least five new binary phases have been found. The crystal structure of NpGe2−x (defect ThSi2 type), NpGe2−x (defect AlB2 type), NpGe (USi type), Np5Ge4 (Ti5Ga4 type), and Np5Ge3 (W5Si3 type) have been refined from single-crystal and powder X-ray diffraction data. X-ray powder analyses by Rietveld-type profile refinement revealed a small homogeneity range of the three first phases, as usually observed with the rare-earth or uranium isotypic compounds, whereas Np5Ge4 and Np5Ge3 seem to be line compounds as the unit cell parameters were independent of the starting composition. The formation and the homogeneity range of these new phases are discussed, and the structural evolution is compared with the analogous uranium binary system.

Intermetallic Cerium Compounds with Ordered U3Si2 Type Structure

Abstract New intermetallic cerium compounds Ce2T2Mg (T = Ni, Cu, Pd), C2T2Cd (T=Pd, Pt, Au), and C2T2Pb (T = Pt, Au) were prepared by reaction of the elements in sealed tantalum tubes in a high-frequency furnace. Most C2T2X (X = Mg, Cd, Pb) compounds are stable after annealing at about 1000 K, while Ce2Pd2Mg is obtained as single phase only after melting and quenching. A thermal treatment at about 1000 K leads to decomposition in CePdMg and CePd. The eight compounds were investigated by X-ray diffraction both as powders and single crystals, and most structures were refined from single crystal data. They adopt an ordered U3Si2 type structure with space group P4/mbm: a = 759.6(1), c = 376.71 (9) pm, wR2 = 0.0562, 294 F2 values, 12 parameters for Ce2Ni2Mg, a = 787.41(9), c = 387.23(7) pm, wR2 = 0.0438, 222 F2 values, 12 parameters for Ce2Cu2Mg, a = 777.14(8), c = 400.03(7) pm, wR2 = 0.0276, 221 F2 values, 13 parameters for Ce2Pd2.03Mg0.97, a = 777.90(6), c = 393.28(6) pm, wR2 = 0.0360,317 F2 values, 12 parameters for Ce2Pd2Cd, and a = 779.90(7), c = 389.97(7) pm, wR2 = 0.0453, 315 F2 values, 12 parameters for Ce2Pt2Cd. Refinement of the occupancy parameters revealed full occupancy for most sites. A mixed palladium/magnesium (97 % Mg / 3 % Pd) occupancy was observed only for the 2a site of Ce2Pd2.03Mg0.97, indicating a small homogeneity range for this compound. Ce2Au2Cd (a = 804.93(7), c =393.36(6) pm) and the plumbides Ce2Pt2Pb (a = 794.63(7), c = 381.50(6) pm) and Ce2Au2Pb (a = 810.70(7), c = 394.85(7) pm) were characterized through their Guinier powder data. The structures of the Ce2T2X compounds can be interpreted as an intergrowth of distorted AIB2 and CsCl related slabs of compositions CeT2 and CeX. The course of the lattice parameters and chemical bonding within the series of Ce2T2X compounds are briefly discussed.

Structure and Properties of Sr2Au3In4 and Eu2Au3In4

Sr2Au3In4 was synthesized by reacting the elements in glassy carbon crucibles under an argon atmosphere in a high-frequency furnace. Eu2Au3In4 was obtained in the same way but starting with EuAuIn as a precursor and admixing indium and gold. Both compounds were investigated by X-ray diffraction on powders and single crystals: anti-Hf2Co4P3 type, P62m, a=1501.6(9) pm, c=457.9(2) pm, wR2=0.0734, 1030 F2 values, 45 variables for Sr2Au2.85In4.15 and a=1489.7(3) pm, c= 454.90(7) pm, wR2=0.1222, 1051 F2 values, 45 variables for Eu2Au3In4. One gold site in the strontium compound shows a mixed occupancy with indium atoms indicating a small homogeneity range according to Sr2Au3−xIn4+x. Striking structural motifs of Sr2Au3In4 and Eu2Au3In4 are gold-centered trigonal prisms formed by the strontium (europium) and indium atoms. All gold atoms have coordination number 9 in the form of tricapped trigonal prisms. The indium atoms in Sr2Au3In4 and Eu2Au3In4 occupy the cobalt positions of the Hf2Co4P3 type and the more electronegative gold atoms take the phosphorus positions, indicating that Sr2Au3In4 and Eu2Au3In4 may be considered as ternary aurides. The gold and indium atoms form three-dimensional [Au3In4]4− polyanions in which the divalent strontium and europium atoms occupy distorted hexagonal tubes. Magnetic susceptibility measurements of Eu2Au3In4 show paramagnetic behavior above 50 K with an experimental magnetic moment of 7.88(5) μB/Eu indicating Eu2+. Antiferromagnetic ordering is detected at 9.5(5) K at low external fields. A metamagnetic transition is observed at 2 K at a critical field of 0.5(2) T. The experimental saturation moment at 2 K and 5.5 T is 5.95(5) μB/Eu. Electrical conductivity investigations exhibit metallic behavior with a room temperature value of 75±10 μΩcm for the specific resistivity. 151Eu Mössbauer spectroscopic measurements show a broadened line with an isomer shift of −10.5(5) mm/s at 78 K in accordance with several sites of divalent europium. Below 10 K magnetic hyperfine field splitting is observed.