Small Homogeneity Range Research Articles

Subsolidus phase diagrams of the In2O3-SnO2-ZnO system at 1400 and 1500 °C and new ternary In2Sn2Zn2O9 phase

The In2O3-SnO2-ZnO system is important for the transparent conducting oxides. The isothermal phase diagrams of the ternary In2O3-SnO2-ZnO system at 1400 and 1500 °C were experimentally studied by quenching experiments followed by XRD and EPMA phase analysis. A new ternary In2Sn2Zn2O9 phase with crystal structure analogous to R3c ZnSnO3 was found, and its eutectoid decomposition reaction to In2O3 bixbyite s.s. + Zn2SnO4 spinel s.s. + SnO2 was determined to be 1310 ± 10 °C. In addition, a small homogeneity range of this ternary phase toward In2O3 was found: In2+2xSn2-xZn2-xO9 where x = 0.0 ∼ 0.2 by Zn2+ + Sn4+ = 2 In3+ substitution.

APd2Zn3 (A=Ca, Sr, Eu) with a CaCu5 superstructure

AbstractThe intermetallic phases APd2Zn3 (A=Ca, Sr, Eu) were synthesized from the elements in sealed niobium ampules in an induction furnace. The phase purity of the samples was checked by powder X‐ray diffraction (Guinier technique). The structures were refined from single crystal X‐ray diffractometer data: YNi2Al3 type (CaCu5 superstructure), P6/mmm, a=936.97(4), c=420.75(2) pm, wR2=0.0206, 259 F2 values, 17 variables for CaPd2Zn3, a=953.63(6), c=425.38(3) pm, wR2=0.0185, 230 F2 values, 17 variables for SrPd2Zn3 and a=948.20(7), c=423.20(3) pm, wR2=0.0209, 228 F2 values, 18 variables for EuPd2.12(1)Zn2.88(1). The europium‐based crystal showed a small homogeneity range through Pd/Zn mixing. The striking structural motifs of the APd2Zn3 phases are Kagome networks formed by the palladium and zinc atoms. The superstructure formation (discussed on the basis of a Bärnighausen tree) results from a different Pd/Zn coloring and a shift of one A position by c/2. The divalent character of europium in EuPd2Zn3 was substantiated by magnetic susceptibility and 151Eu Mössbauer spectroscopic measurements. EuPd2Zn3 orders ferrimagnetically at TC=17.5(5) K. The magnetization behavior at 3 K (two‐step magnetization) confirms the existence of two crystallographically independent europium sites. The 151Eu Mössbauer spectrum at 5 K shows full magnetic hyperfine field splitting (δ=−8.99(4) mm s−1 and BHf=27.7(1) T).

Intermetallic phases in the Sc–Ir–In system – synthesis and structure of Sc1.024Ir2In0.976 and Sc3Ir1.467In4

Abstract The intermetallic scandium compounds Sc1.024Ir2In0.976 and Sc3Ir1.467In4 were synthesized by reactions of the elements in sealed tantalum ampoules at high temperature followed by annealing for crystal growth. Both structures were refined from single-crystal X-ray diffractometer data: MnCu2Al type, F m 3 ‾ m $Fm‾{3}m$ , a = 639.97(19) pm, wR2 = 0.0376, 41 F 2 values, seven variables for Sc1.024Ir2In0.976 and P 6 ‾ $P‾{6}$ , a = 769.99(5), c = 684.71(4) pm, wR2 = 0.0371, 967 F 2 values, 33 variables for Sc3Ir1.467In4. Sc1.024Ir2In0.976 is a new Heusler phase with a small homogeneity range due to Sc/In and In/Sc mixing. The structure of Sc3Ir1.467In4 is closely related to that of Sc3Rh1.594In4 and belongs to the large family of ZrNiAl superstructures. The striking structural motif is the ordered stacking of empty In6 and filled Ir@In6 prisms with Ir–In distances of 269 pm.

Isothermal section of the Ho-Cо-Sn system at 770 K

The phase equilibrium diagram of the Ho - Co - Sn ternary system was constructed over the whole concentration range at 770 K using methods of powder X-ray diffractometry, metallography and electron microprobe analysis. The alloys for investigation were prepared by direct arc melting the stoichiometric amounts of the constituent elements under high purity Ti-gettered argon atmosphere on a water-cooled copper bottom. The arc-melted ingots were then annealed at 770 K in evacuated quartz glass tubes for two months and subsequently cold water quenched. The synthesized and annealed samples are stable in atmospheric conditions. For the characterization of the annealed samples X-ray powder diffraction on DRON-2.0m diffractometer with Fe K α-radiation was performed. The chemical and phase compositions of the obtained samples were examined by Scanning Electron Microscopy REMMA-102-02 electron microscope. Interaction of holmium with nickel and tin at 770 K resulted in the formation of eight ternary intermetallic compounds: Ho 6 Co 2 Sn (Ho 6 Co 2 Ga-type), Ho 3 Co 8 Sn 4 (Lu 3 Co 7 . 77 Sn 4 -type), HoCoSn (TiNiSi-type), Ho 3 Co 6 Sn 5 (Dy 3 Co 6 Sn 5 -type), Ho 117 Co 57 . 3 Sn 111 . 5 (Dy 117 Co 57 Sn 112 -type), HoCo 6 Sn 6 (YCo 6 Ge 6 -type), Ho 5 Co 6 Sn 18 (Er 4 Rh 6 Sn 19 -type), and Ho 7 Co 6 Sn 23 (Ho 7 Co 6 Sn 23 -type). The Ho 3 Co 8 Sn 4 compound is characterized by small homogeneity range along isoconcentrate of Ho up to 4 at. % Sn. According to EPMA data the homogeneity range of the Ho 3 Co 8 Sn 4 compound is limited by Ho 20 .58 Co 52 . 3 1 Sn 27 .1 1 and Ho 21 .0 6 Co 5 6.7 8 Sn 2 2.1 6 compositions. Ho 7 Co 6 Sn 23 compound was checked using differential thermal analysis (LINSEIS STA PT 1600 device). The DTA curve measured in the heating regime shows the thermal peak at about 980 K which can be associated with the decomposition of the Ho 7 Co 6 Sn 23 phase. In the Ho–Sn, Co-Sn and Ho-Co systems a formation of the all binaries reported in the literature was confirmed. Additionally under used conditions the HoCo 5 binary with CaCu 5 -type was identified in the Ho-Co system. The formation of the interstitial-type solid solution HoCo x Sn 2 based on HoSn 2 (ZrSi 2 -type) binary compound was found up to 10 at. % Co ( а = 0.4382(2), b = 1.6193(4), с = 0.4291(2) nm for HoSn 2 ; а = 0.4393(2), b = 1.6273(7), с = 0.4334(4) nm for Ho 30 Co 10 Sn 60 sample. Solubility of the third component in other binary compounds is less than 1-2 at. %. With regard on the stoichiometry and crystal structure of the formed intermediate phases the investigated Ho-Co-Sn ternary system is similar to the Y-Co-Sn, Dy-Co-Sn and Er-Co-Sn systems. Keywords: intermetallics, ternary system, phase equilibria.

Rare earth-copper-magnesium intermetallics: crystal structure of CeCuMg, magnetocaloric effect of GdCuMg and physical properties of the Laves phasesRECu4Mg (RE=Sm, Gd, Tb, Tm)

AbstractThe intermetallic magnesium compounds CeCuMg and GdCuMg as well as the ternary Laves phasesRECu4Mg (RE=Sm, Gd–Tm) were synthesized from the elements by different annealing sequences in high-frequency and muffle furnaces using niobium ampoules as crucibles. All samples were characterized through the lattice parameters using X-ray powder diffraction (Guinier technique). Two structures were refined from single-crystal X-ray diffractometer data:a=764.75(6),c=414.25(4) pm, space groupP6̅2m,wR2=0.0389, 338F2values, 15 parameters for CeCuMg (ZrNiAl type) anda=723.18(2) pm, space groupF4̅3m, wR2=0.0818, 91F2values, eight parameters for Gd1.06(3)Cu4Mg0.94(3)(MgCu4Sn type). The Laves phase shows a small homogeneity range (Gd/Mg mixing). An investigation of the magnetocaloric effect (MCE) of ferromagnetic GdCuMg (ZrNiAl type;TC=82 K) revealed a magnetic entropy change of ΔSM=6.5 J kg−1K−1and a relative cooling power of RCP=260 J kg−1for a field change from 0 to 70 kOe, classifying GdCuMg as a moderate magnetocaloric material for theT=80 K region. Of the Laves phasesRECu4Mg, SmCu4Mg shows van-Vleck paramagnetism above a Néel temperature of 10.8(5) K, whereas GdCu4Mg and TbCu4Mg undergo antiferromagnetic phase transitions at about 48 and 30 K, respectively. TmCu4Mg shows Curie-Weiss behavior in the entire temperature range. The electrical resistivity of SmCu4Mg and the specific heat capacity of GdCu4Mg were measured for further characterization.

A computational search for the zeta phase in the tantalum carbides

AbstractA systematic electronic structure density functional theory search for the zeta phase in the tantalum carbon system has been conducted, demonstrating that the zeta phase does indeed lie on the convex hull, establishing low‐temperature thermodynamic stability, and is structurally stable. Even though the zeta phase is most oft reported as a ζ‐Ta4C3‐x structure, these new computational results reveal that the perfectly ordered zeta phase occurs at the Ta3C2 composition and belongs to the C2/m space group. Furthermore, these results suggest that the space group may be a result of an order‐disorder transition and potential deviations from ideal stoichiometry at higher temperatures. The structure of this Ta3C2 compound can be described as ordered strings of carbon vacancies on a single carbon plane, which is also the preferred plane where additional carbon vacancies or interstitials form. These defects have modest formation energies, which provides further explanation for the small homogeneity range in zeta phase.

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 RE 9CoMg4 (RE=Y, Dy-Tm, Lu)

Abstract Six new rare earth metal-rich intermetallic compounds RE 9CoMg4 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 F 2 values, 20 variables for Y9CoMg4 and a=945.20(4), c=953.11(5) pm, wR2=0.0358, 585 F 2 values, 21 variables for Tm8.56CoMg4.44 (a small homogeneity range results from Tm/Mg mixing). The RE 9CoMg4 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.

Interaction of tantalum, titanium and phosphorus at 1070 K: Phase diagram and structural chemistry

The solid state phase diagram for the equilibria of the ternary Ta-Ti-P system was established by X-ray powder diffraction at T = 1070 K in the region up to 67 at.% P. Isostructural compounds Ta3P and Ti3P (both Ti3P-type) form a continuous series of substitution-type solid solutions. The majority of binary compounds form substitution-type solid solutions, in which the substitution of Ti for Ta, or Ta for Ti, takes place. The crystal structure investigation of the new ternary phosphide demonstrates that this phase is isotypical to the OsGe2 structure type and has a small homogeneity range, which can be described by the formula Та1-xТіxР2 (x = 0.07(3)−0.145(7), space group C2/m, a = 8.8556(9)−8.8446(2), b = 3.2654(4)−3.2605(1), c = 7.4846(8)−7.4741(1) Å, β = 119.307(2)−119.308(1)°). Our density functional theory (DFT) electronic structure calculations show that the stoichiometric composition TaP2 has no electronic instability, although it does not exist under the thermal conditions used in present study. The addition of a small amount of Ti leads to a ternary phase Та1-xТіxР2 (x = 0.07(3)−0.145(7)) with a higher thermal stability compared to TaP2.

Synthesis and crystal structure of mixed metal(III) tungstenyl(VI) ortho-pyrophosphates

The series of isotypic anhydrous ortho-pyrophosphates MIII(WVIO2)2(P2O7)(PO4) (M: Sc, V, Cr, Fe, Mo, Ru, Rh, In, Ir) was obtained via vapor phase moderated solid state reactions in sealed ampoules. The crystal structure of the phosphates MIII(WVIO2)2(P2O7)(PO4) (M: V, Ru, Rh) was solved from single crystal X-ray data (C2/c, Z = 16). Fairly regular MO6 and distorted WO6 octahedra share vertices with PO4 and P2O7 units to form a 3D network. For the ortho-pyrophosphates with M: V3+, Cr3+, and Fe3+ the oxidation state of M is confirmed by magnetic measurements. 31P-MAS-NMR spectra of the diamagnetic phosphates MIII(WVIO2)2(P2O7)(PO4) (M: Sc, In, Ir) show surprisingly different isotropic chemical shifts for the seven phosphorus sites. VIII(WVIO2)2(P2O7)(PO4) occurs as equilibrium phase in the quasi-binary system (V1–xWx)OPO4 at x = 0.67 and exhibits a small homogeneity range 0.60 ≤ x ≤ 0.67. The scandium compound shows a fully inverted occupancy of the M sites according to the formulation W(Sc1/2W1/2O2)2(P2O7)(PO4).

Ca4Au10Zn3 – A Substitution Variant of AlB2 by Incorporation of Zn3 Triangles

AbstractThe gold‐rich intermetallic phase Ca4Au10Zn3 was synthesized from the elements by high‐frequency melting in sealed tantalum ampoules. Analyses of the sample by X‐ray powder and single crystal diffraction indicated a new structure type with a small homogeneity range resulting from Au/Zn mixing: C2/c, a = 1598.4(2), b = 819.7(1), c = 1188.2(2) pm, β = 120.93(1)°, wR2 = 0.0397, 2292 F2 values, 83 variables for Ca4Au9.66(1)Zn3.34(1), and a = 1596.6(2), b = 818.8(2), c = 1187.1(2) pm, β = 120.91(2)°, wR2 = 0.0280, 2296 F2 values, 83 variables for Ca4Au9.98(1)Zn3.02(1). The gold atoms built up a three‐dimensional distorted tetrahedral network with Au–Au distances ranging from 274–294 pm. The cavities within this network are filled by calcium atoms and Zn3 triangles (272–279 pm Zn–Zn) in an ordered manner. The small homogeneity range Ca4Au10–xZn3+x concerns Au/Zn mixing within the triangles and the tetrahedral network as well. The crystal chemical relationship with the aristotype AlB2 is discussed on the basis of a group‐subgroup scheme.

Investigation of phase equilibria in the quaternary Ce–Mn–In–Ge system and isothermal sections of the boundary ternary systems at 800 °C

Part of the quaternary Ce–Mn–In–Ge phase diagram has been examined through powder X-ray diffraction and energy-dispersive X-ray analysis. Two new quaternary (Ce4Mn2InGe4 and Ce2Mn2InGe2) and two ternary (Ce3Mn2Ge3 and Ce43Mn18Ge39) phases were found. The isothermal sections of the boundary ternary systems (Ce–Mn–In, Mn–In–Ge, Ce–In–Ge, and Ce–Mn–Ge) were determined at 800°C. Among these, the Ce–Mn–Ge system deserves particular attention because the phase equilibria are complex. Relative to the previously reported phase diagram evaluated at a lower temperature (400°C), three ternary phases (CeMn2Ge2, Ce2MnGe6, and CeMnGe) persist, Ce2MnGe5 does not form, and two new phases with very close composition (Ce3Mn2Ge3 and Ce43Mn18Ge39) appear at 800°C. Ce3Mn2Ge3 (orthorhombic Hf3Ni2Si3-type) has a small homogeneity range (2%) deviating from the ideal composition, whereas Ce43Mn18Ge39 (tetragonal La2+xMnGe2+y-type) has negligible homogeneity. Magnetic measurements on Ce4Mn2InGe4 suggest ferromagnetic behaviour.

Interaction of yttrium with nickel and phosphorus: Phase diagram and structural chemistry

The interaction between the components of the ternary Y–Ni–P system has been investigated by means of electron probe microanalysis, X-ray phase and structure analyses, and the isothermal section of the phase diagram at 1070 K has been constructed for the first time. Existence of the earlier reported eight ternary phosphides of yttrium and nickel was confirmed, among them seven ternaries are daltonide compounds: YNi4P2 (ZrFe4Si2-type structure), Y2Ni12P7 (Zr2Fe12P7-type structure), Y6Ni20P13 (Zr6Ni20P13-type structure), Y6Ni14.9P10.18 (own structure type), Y20Ni42P30.34 (Sm20Ni41.6P30-type structure), Y15Ni28P21 (Tb15Ni28P21-type structure), and YNiP (Tb1−xNiP-type structure), whereas YNi1.66−1.78P2 (ThCr2Si2-type structure) is a berthollide compound with small homogeneity range. The crystal structures of the some ternary phosphides have been determined by X-ray powder diffraction (YNi4P2 and YNi1.66−1.78P2) and single crystal diffraction (Y2Ni12P7) techniques.

Correlations between Chemical Bonding and Magnetic Exchange Interactions: Synthesis, Crystal Structures, and Magnetic Properties of the New Family RE2AlGe2 (RE = Tb–Tm, Lu)

Six new rare-earth metal germanides with general formula RE2Al(1-x)Ge(2+x) (RE = Tb-Tm, Lu; 0.13(2) ≤ x ≤ 0.37(2)) have been synthesized by direct fusion of the corresponding elements. Their structures have been established by single-crystal diffraction to crystallize with the orthorhombic space group Immm (no. 74), adopting the W2CoB2 structure type. The Al and Ge atoms are arranged in alternating planar layers, made of rhombic- and hexagonal-fragments. The rare-earth metal substructure consists of puckered four-connected nets. Electronic structure calculations support the coloring of the Ge and Al sites and account for the existence of a small homogeneity range. DC magnetization measurements for all specimens are also presented; based on the RKKY and mean-field theories for antiferromagnets, relationships between the chemical bonding and exchange interactions are discussed.

CaTMg2 and CaTCd2 (T =Rh, Pd, Pt) with YPd2Si-type Structure

The intermetallic calcium compounds CaTMg2 and CaTCd2 (T =Rh, Pd, Pt) were obtained by high-frequency melting of the elements in sealed niobium ampoules or through reactions in muffle furnaces. The polycrystalline samples were characterized by powder X-ray diffraction. They crystallize with a site occupancy variant of YPd2Si, a ternary ordered version of Fe3C. The structures of CaPdMg2 and CaPdCd2 were refined from single-crystal diffractometer data: Pnma, a=792.2(2), b=803.4(2), c=572.0(1) pm, wR2=0.0663, 1621 F2 values, 24 variables for Ca0:94PdMg2:06 and a=794.6(2), b=809.5(3), c=554.7(2) pm, wR2=0.0301, 819 F2 values, 23 variables for CaPdCd2. A small range of homogeneity was observed for Ca1-xPdMg2+x. The magnesium and cadmium atoms build up three-dimensional tetrahedral substructures (306 - 327 pm Mg-Mg and 307 - 317 pm Cd-Cd) that resemble hexagonal diamond, lonsdaleite. Together with the palladium atoms one obtains three-dimensional, covalently bonded [PdMg2] and [PdCd2] networks which leave cages for the calcium atoms. The latter are bonded to these networks via shorter Ca-Pd contacts (298 - 319 pm in Ca0:94PdMg2:06 and 295 - 312 pm in CaPdCd2). The course of the interatomic distances is in line with calculated overlap populations. The CaPdMg2, SrPdMg2 and CaRhIn2 structures are all derived from a CaIn2-related subcell by an ordered filling of transition metal atoms into trigonal prisms. This leads to different herringbone patterns for the networks of puckered and elongated hexagons of magnesium and indium atoms.

Ferromagnetism and superconductivity in CeFeAs1−xPxO (0≤x≤40%)

We report on superconductivity in CeFeAs1-xPxO and the possible coexistence with Ce- ferromagnetism (FM) in a small homogeneity range around x = 30% with ordering temperatures of T_SC = T_C = 4K. The antiferromagnetic (AFM) ordering temperature of Fe at this critical concentration is suppressed to T^N_Fe ~ 40K and does not shift to lower temperatures with further increase of the P concentration. Therefore, a quantum-critical-point scenario with T^N_Fe -> 0K which is widely discussed for the iron based superconductors can be excluded for this alloy series. Surprisingly, thermal expansion and X-ray powder diffraction indicate the absence of an orthorhombic distortion despite clear evidence for short range AFM Fe-ordering from muon-spin-rotation measurements. Furthermore, we discovered the formation of a sharp electron spin resonance signal unambiguously connected with the emergence of FM ordering.

The ternary system Au–Ba–Si: Clathrate solution, electronic structure, physical properties, phase equilibria and crystal structures

We report on (i) the phase relations at 800°C within the ternary system Au–Ba–Si up to 33.3at.% Ba, (ii) on the crystallographic data of new ternary compounds, (iii) on details of the clathrate type I solid solution, (iv) on electrical and thermal transport measurements for Ba8Au5.1Si40.9 supported by (v) density functional theory calculations. The clathrate type I solid solution Ba8AuxSi46−x at 800°C extends from Ba8Au4Si42 (a=1.039nm) to Ba8Au6Si40 (a=1.042nm). The cubic primitive symmetry (space group Pm3¯n) was confirmed by X-ray powder diffraction in the whole homogeneity region. The lattice parameters of the solid solution show an almost linear increase with increasing gold content and site preferences from X-ray refinement confirm that gold atoms preferably occupy the 6d site in random mixture with Si atoms. The phase equilibria at 800°C are characterized by seven ternary phases in the investigated region up to 33.3at.% Ba. The homogeneity range has been established for Ba(Au1−xSix)2 (AlB2 type, extending from BaAu0.4Si1.6 to BaAu0.9Si1.1). BaAu2+xSi2−x (unknown structure type) exhibits a very small homogeneity range (x=0.6–0.7) and two other ternary phases exist at about 22at.% Ba, 52at.% Au and 28at.% Si and 20at.% Ba, 58at.% Au and 22at.% Si (structure types for both unknown). The crystal structures of two further novel phases in the gold-rich part have been determined from single crystal X-ray data: BaAu3+xSi1−x of BaAu3Ge type (x=0–0.3, space group P4/nmm, x=0: a=0.6488(2), c=0.5305(2) nm) and BaAu5−xSi2+x (x=0–0.2, own structure type, space group Pnma, x=0: a=0.8935(2), b=0.6939(2), c=1.0363(2)nm). The proximity of Ba8AuxSi46−x to a metal to insulator transition is corroborated by density functional theory electronic structure calculations. A gap in the electronic density of states, located near the Fermi energy, gives rise to distinct features of the temperature-dependent electrical resistivity and Seebeck effect.

The Gold-rich Indide Eu5Au17.7In4.3 and its Relation with the Structures of SrAu4.76In1.24 and BaLi4

The gold-rich indide Eu5Au17.7In4.3 was synthesized from the elements in a sealed tantalum ampoule that was heated in a high-frequency furnace. Eu5Au17.7In4.3 crystallizes with a new monoclinic structure type: C2/m, a = 902.7(2), b = 722.8(3), c = 1734.1(4) pm, β = 94.31(3)°, wR2 = 0.0907, 2640 F2 values and 74 variables. Eu5Au17.7In4.3 has a pronounced gold substructure with Au-Au distances ranging from 278 to 300 pm. The striking structural motifs in the gold substructure are networks of Au6 hexagons and discrete units of corner- and edge-sharing Au4 tetrahedra. Eu5Au17.70In4.30 exhibits a small homogeneity range with In/Au mixing on two Wyckoff sites. Geometrically, the Eu5Au17.7In4.3 structure can be explained as an intergrowth variant of slightly distorted SrAu4.76In1.24- and BaLi4-related slabs. The europium coordination in the BaLi4 slabs is similar to binary EuAu2.

The Shape of Nitrogen Concentration-Depth Profiles in γ′-Fe4N1–z Layers Growing on α-Fe Substrates; the Thermodynamics of γ′-Fe4N1–z

An unusual, concave curvature is observed in experimental nitrogen concentration-depth profiles in the surface region of γ′-Fe4N1–z layers obtained during nitriding pure iron at 823 K and 843 K (550 °C and 570 °C). It can be shown by the simulation of nitrogen concentration-depth profiles in γ′-layers, adopting the thermodynamic Wagner-Schottky approach applied to γ′-Fe4N1–z, that this concave character is caused by the strong concentration dependence of the Gibbs energy of the γ′-phase, which is counterintuitive in recognition of the very small homogeneity range of γ′ iron nitride. Thereby, for γ′-layers with low porosity, a previous suggestion ascribing the concave shape to the additional uptake of nitrogen through porous grain-boundary channels is rendered less likely.

A new phase in the system lithium–aluminum: Characterization of orthorhombic Li 2Al

Investigation of the Li rich part of the binary Li–Al system revealed the existence of a new phase, orthorhombic Li 2Al, which is isostructural to Li 2Ga and Li 2In. The crystal structure was determined from single crystal X-ray diffraction data ( Cmcm, a=4.658(2) Å, b=9.767(4) Å, c=4.490(2) Å, Z=4). Refinement of atomic position site occupancies yielded a composition Li 1.92Al 1.08 (64 at% Li) indicating a small homogeneity range, Li 2− x Al 1+ x . Li 2Al is the peritectic decomposition product of the stoichiometric compound Li 9Al 4, which is stable below 270±2 °C. Li 2Al itself decomposes peritectically to Li 3Al 2 and Li rich melt at 335±2 °C. The discovery of Li 2Al (Li 2− x Al 1+ x ) settles a long standing inconsistency in the Li–Al phase diagram which was based on the assumption that Li 9Al 4 possesses a high temperature modification.

Modulated Lanthanum Chains in the Crystal Structure of La3.65[Ru(C2)3

AbstractLanthanum ruthenium carbide La3.65[Ru(C2)3] crystallizes hexagonal (P63/m) with a = 887.9(2) pm and c = 1606.8(6) pm, V = 1096.8(4)·106 nm3, and Z = 6. The crystal structure contains trigonal‐planar Ru(C2)3 groups and lanthanum atoms, which form a partial structure of the chemical composition La3Ru(C2)3. Additional lanthanum atoms occupy hexagonal channels built by those carbon atoms of the C2 ligands, which are non‐bonded to the central ruthenium atoms. The distribution of these lanthanum atoms along the c axis results in a threefold superstructure, which was refined as a commensurate modulated structure (P63/m (00g)s0, q = (0, 0, {}^1/{}_3)). Harmonic occupational and displacive modulation functions were used for the structure refinement. The structure converged to R1 = 4.9 % for all data (R1 = 2.6 % for the main reflections, R1 = 11.1 % for the 1st order satellite reflections). A small homogeneity range for this phase is predicted by total energy calculations using the PAW‐GGA method (VASP). Chemical bonding analysis reveals that the C2 pairs are best described as acetylide C22– units.