On the crystal structure of new series of compounds, RPt2+xSb2−y (x = 0.125, y = 0.25; R = La, Ce, Pr)

A new compound CePt_2+xSb_2−y (x = 0.125, y = 0.25) was synthesized by arc-melting of the elements. The chemical and structural characterizations were carried out at room temperature on as-cast samples using X-ray diffractometry, metallographic analysis and EDS-microanalysis. According to the results of X-ray single crystal diffraction this antimonide crystallizes in I4cm space group (no. 108), Z = 32, ρ = 12.19 Mg/m³, μ = 89.05 mm⁻¹ (a = 12.5386(3) Å, c = 21.4692(6) Å (crystal I) and a = 12.5455(2) Å, c = 21.4791(5) Å (crystal II)). The structure and composition were confirmed by powder X-ray diffraction (a = 12.4901(2) Å, c = 21.3620(4) Å) and EDS-microanalysis respectively. Isotypic compounds were observed with La and Pr from X-ray powder diffraction of as-cast alloys at room temperature (a = 12.6266(4) Å, c = 21.4589(6) Å for LaPt_2+xSb_2−y and a = 12.5184(5) Å, c = 21.4178(7) Å for PrPt_2+xSb_2−y). The CePt_2+xSb_2−y structure is derived from CaBe₂Ge₂ (a = 2a₀ − 2b₀, b = 2a₀ + 2b₀, c = 2c₀) and comprises a new atomic arrangement with both vacancy on 4(b) pyramidal site and substitution of antimony atoms (X) by platinum (B) in the B–XX–B layers (referring to the subcell structure) forming two B––1/2B1/2XX–3/4B and two X–BB–X layers per cell. The structure of CePt_2+xSb_2−y is compared with those reported before for URh_1.6As_1.9 and CeNi_1.91As_1.94.     

Synthesis and crystal structure of CaAgBi and BaAg1.837Bi2

Two ternary alkali earth silver bismuthides, CaAgBi and BaAg_1.837Bi₂, have been synthesized by solid-state reactions of the corresponding metals in welded Nb tubes at high temperature. Their structures have been established by single-crystal X-ray diffraction studies. CaAgBi crystallizes in the hexagonal space group P6₃mc (No.186) with cell parameters of a = b = 4.8113(4) Å, c = 7.8273(9) Å, V = 156.92(3) Å³, and Z = 2. BaAg_1.837Bi₂ belongs to tetragonal space group P4/nmm (No.129) with cell parameters of a = b = 4.9202(2) Å, c = 11.628(1) Å, V = 281.50(3) Å³, and Z = 2. The structure of CaAgBi is of the LiGaGe type, and features a three-dimensional four-connected (3D4C) anionic network with Ca²⁺ encapsulated in the channels formed by [Ag₃Bi₃] six-membered rings. BaAg_1.837Bi₂ is isostructural with CaBe₂Ge₂, a variant of the tetragonal ThCr₂Si₂-type structure. Its structure exhibits a three-dimensional anionic network built of (0 0 1) and (0 0 2) puckered [Ag₂Bi₂] layers interconnected via additional Ag–Bi bonds along the c-axis. BaAg_1.837Bi₂ is metallic based on band structure calculations.     

An investigation of the structures of the compounds in the tin-rich part of the Dy–Sn system: Crystal structure of Dy5Sn11 and Dy5Sn13

The structural properties of the compounds in the tin-rich part of the dysprosium–tin system have been studied by X-ray powder diffraction. The crystal structures of six compounds DySn_2+x (0 < x < 1) have been characterized. There are four compounds with known structural types: DySn₂ with the ZrSi₂ structure, Dy₃Sn₇ with the Gd₃Sn₇ structure, Dy₂Sn₅ with the Er₂Ge₅ structure, DySn₃ with the DyGe₃ structure and two compounds characterized by new body-centred orthorhombic types (Immm): Dy₅Sn₁₁ (a = 4.411 Å, b = 42.50 Å and c = 4.328 Å) and Dy₅Sn₁₃ (a = 4.341 Å, b = 48.05 Å and c = 4.405 Å) which result from various insertions of AuCu₃ and Po slabs into the ZrSi₂ structure. The relationships and structural evolution are discussed.     

Crystal structure of the R3Si1.25Se7 (R = Pr, Nd and Sm) compounds

The crystal structure of new ternary R₃Si_1.25Se₇ (R = Pr, Nd and Sm) compounds (Dy₃Ge_1.25S₇ structure type, Pearson symbol hP22.5, space group P6₃, a = 1.05268 (3) nm, c = 0.60396 (3) nm, R_I = 0.0897 for Pr₃Si_1.25Se₇; a = 1.04760 (3) nm, c = 0.60268 (3) nm, R_I = 0.0891 for Nd₃Si_1.25Se₇; a = 1.04166 (6) nm, c = 0.59828 (6) nm for Sm₃Si_1.25Se₇) was determined using X-ray powder diffraction. The nearest neighbours of the R and Si atoms are exclusively Se atoms. The latter form distorted trigonal prisms around the R atoms, octahedra around the Si1 atoms and tetrahedra around the Si2 atoms. Tetrahedral surrounding exists for Se1 and Se3 atoms. Six neighbours surround every Se2 atom.     

Two polymorphs of Ba3Sn2P4: Single crystal and electronic structures

Two polymorphs (I and II) of Ba₃Sn₂P₄ have been found in the same preparative batch. Both compounds crystallize in the centrosymmetric monoclinic space group P2₁/c (#14, a = 7.8669(2) Å, b = 19.2378(5) Å, c = 7.8472(2) Å, β = 112.77(1)°, V = 1095.06(5) Å³, Z = 4, and R/wR = 0.0303/0.0710 for I; a = 7.8771(3) Å, b = 19.4099(7) Å, c = 7.7040(3) Å, β = 112.44(1)°, V = 1088.67(7) Å³, Z = 4, and R/wR = 0.0224/0.0415 for II). Both structures consist of one-dimensional chains separated by Ba²⁺ cations. The isolated chain consists of condensed ethane-like [Sn₂P₆] units. In polymorphs I and II, the condensation and connectivity of the [Sn₂P₆] units are quite different. While [Sn₂P₆] units form four- and six-membered rings in I, they form the five-membered rings in II. The electronic structure calculations indicate that semiconducting behavior is expected for both compounds.     

Structural investigation of the alluaudite-like mixed-valence iron phosphate: Na1.25Mg1.10Fe1.90(PO4)3

A new mixed-valence iron phosphate Na_1.25Mg_1.10Fe_1.90(PO₄)₃ has been synthesized as single crystals by a flux technique and its structure has been refined from X-ray data to a residual R₁ = 0.032. The compound crystallizes in the monoclinic space group C2/c with the parameters: a = 11.7831(3) Å, b = 12.4740(3) Å, c = 6.3761(2) Å, β = 113.643(2)° and Z = 4. The structure belongs to the alluaudite structural type, and thus it obeys to the X(2)X(1)M(1)M(2)₂(PO₄)₃ general formula. The X(2) and X(1) sites are occupied by sodium while the M(1) and M(2) sites feature a statistical distribution of iron and magnesium.

Additional information about the cation distribution has been extracted from a Mössbauer spectroscopy study which confirmed the mixed valency of the compound. A magnetic susceptibility study has also been undertaken and has shown the compound to be antiferromagnetic with a Neel temperature of about 35 K.     

Synthesis and structure of a potassium nitridoditungstenate (K6W2N4O3), a potassium digermanate (K6Ge2O7) and a rubidium digermanate (Rb6Ge2O7)

Light yellow single crystals of potassium nitridoditungstate (K₆W₂N₄O₃) and pale single crystals of potassium digermanate (K₆Ge₂O₇) were obtained by the reaction of the metal oxides WO₃ (molar ratio, 1 : 15.7) or GeO₂ (molar ratio, 1 : 2) in alkali metal amide melts in an autoclave at 530–600 °C for 6–8 days. Colourless single crystals of rubidium digermanate (Rb₆Ge₂O₇) were prepared by the reaction of GeO₂ with rubidium amide (molar ratio, 1 : 2) in ammonia at 350 °C in a high-pressure autoclave (H. Jacobs and D. Schmidt, in E. Kaldis (ed.), High-pressure Ammonolysis in Solid State Chemistry, Current Topics in Materials Science, Vol. 8, North Holland, Amsterdam, 1981, p. 379) (p(NH₃) = 5.5 kbar) for 10 days. In all three cases other nitrogen-containing products were present.

The structures of the title compounds were determined on the basis of single-crystal data. They are isotypic or structurally closely related to each other: K₆W₂N₄O₃: P2₁/n, a = 6.720(2) Å, b = 9.473(1) Å, c = 9.581(2) Å, β = 91.99(2)°, Z = 2, R/R_w = 0.040/0.048, N(I) > 3σ(I) 2057, N(Var.) = 71. K₆Ge₂O₇: Pn, a = 6.529(2) Å, b = 9.079(4) Å, c = 9.162(6)Å, β = 91.85(4)°, Z = 2, R/R_w = 0.022/0.024, N(I) 3σ(I) = 1486, N(Var.) = 135. Rb₆Ge₂O₇: P2₁/n, a = 6.839(4) Å, b = 9.437(6) Å, c = 9.460(6) Å, β = 91.53(5)°, Z = 2, R/R_w = 0.061/0.074, N(I) 3σ(I) = 1055, N(Var.) = 71.     

Ce(Au,Sb)2 with UHg2 structure type, a new member of the AlB2 family

A new ternary compound Ce(Au,Sb)₂, with a homogeneity range has been observed from X-ray powder diffraction of as cast alloys, a = 4.743–4.712 Å, c = 3.567–3.768 Å. Its crystal structure was investigated by X-ray diffraction from Ce(Au_1−xSb_x)₂ (x = 0.266) single crystal: CAD-4 automatic diffractometer, Mo K radiation, a = 4.7256(6) Å, c = 3.6711(6) Å, P6/mmm space group, V = 70.997(17) Å³, Z = 1, ρ = 10.732 Mg/m³, μ = 76.369 mm⁻¹, R₁ = 0.0415, wR₂ = 0.0793 for 99 reflections with I > 2σ(I₀). The coordination polyhedron of X (X = 0.734Au + 0.266Sb) atom is a full-capped trigonal prism [XCe₆X₃X₂]. Ce atom is coordinated by 14 atoms: [CeX₁₂Ce₂]. The compound is isotypic with UHg₂ structure, a deformation derivative of AlB₂ structure type. It forms isostructural compounds with La and Pr.     

Crystal structure of La5Ti4GaO17

The crystal structure of La₅Ti₄GaO₁₇ compound synthesized by heat-treatment of the co-precipitated hydroxy-oxalates has been determined by the X-ray powder diffraction. It was found that crystal structure of La₅Ti₄GaO₁₇ belongs to the CaLa₄Ti₅O₁₇-type structure (space group Pmnn, a = 0.3912(1) nm, b = 3.128(1) nm, c = 0.5523(1) nm, Z = 2). The final R_W value is equal to 0.081 for 169 independent reflections.     

Nd11Pd4In9 compound – A new member of the homological series based on AlB2 and CsCl types

The Nd₁₁Pd₄In₉ compound was prepared by arc melting of pure metals under an argon atmosphere. Crystal structure was refined from X-ray single crystal diffractometer data (space group Cmmm, a = 14.843(3), b = 22.284(3), c = 3.7857(6) Å, Z = 2, R_I = 0.0584, 653 F₂ values). It has own structure type and together with Mn₂AlB₂, Cr₃AlB₄, Mo₂FeB₂ and Lu₅Ni₂In₄ structure types belongs to homological series based on AlB₂ and CsCl structure types with common formula R_m+nM_2nX_m.     

Subsolidus phase relation in the system ZnO–Li2O–MoO3

The subsolidus phase relation of the system ZnO–Li₂O–MoO₃ has been investigated by X-ray diffraction (XRD) analyses. The phase diagram has been constructed. There are six binary compounds and one ternary compound in this system. The phase diagram comprises nine three-phase regions. The ternary compound Li₂Zn₂(MoO₄)₃ is refined by the Rietveld method. It belongs to an orthorhombic system with space group Pnma and lattice constants a = 5.1114 Å, b = 10.4906 Å, c = 17.6172 Å.     

The ternary system Na2O–ZnO–WO3: Compounds and phase relationships

The subsolidus phase relationships of ternary system Na₂O–ZnO–WO₃ have been investigated by X-ray diffraction (XRD) and differential thermal analyzer (DTA). All the samples were synthesized in the temperature range from 530 to 850 °C in air. There are one ternary compound and five binary compounds in the Na₂O–ZnO–WO₃ system, which can be divided into eight three-phase regions. The crystal structure of the ternary compound Na_3.6Zn_1.2(WO₄)₃ is determined by single-crystal structure analysis method. It belongs to triclinic system with space group and lattice constants a = 7.237 (5) Å, b = 9.172 (6) Å, c = 9.339 (6) Å and  = 94.920 (4)°, β = 105.772 (9)°, γ = 103.531 (8)°, Z = 2. DTA analyses indicate that the compound Na₂WO₄ is not suitable to be the flux for ZnO crystal growth below 1250 °C, since no liquidus was observed in the system before 1250 °C.     

X-ray investigations of ternary R3Pd4Ge4 samples

Ternary R₃Pd₄Ge₄ samples (R=Nd, Eu, Er) were investigated by means of X-ray single crystal (four circle diffractometer Philips PW1100, MoK radiation) and powder diffraction (MX Labo diffractometer, CuK radiation). The Er₃Pd_3.68(1)Ge₄ compound belongs to the Gd₃Cu₄Ge₄ structure type, space group Immm, a=4.220(2) Å, b=6.843(2) Å, c=14.078(3) Å, R₁=0.0484 for 598 reflections with F_o>4σ(F_o) from X-ray single crystal diffraction data. No ternary R₃Pd₄Ge₄ compound when R is Nd or Eu was observed. The Nd and Eu containing samples appeared to be multiphase. Ternary phases observed in the Nd₃Pd₄Ge₄ and Eu₃Pd₄Ge₄ alloys and their crystallographic characteristics are the following: NdPd₂Ge₂, CeGa₂Al₂ structure type, space group I4/mmm, a=4.3010(2) Å, c=10.0633(2) Å (X-ray powder diffraction data); NdPd_0.6Ge_1.4, AlB₂ structure type, space group P6/mmm, a=4.2305(2) Å, c=4.1723(2) Å (X-ray powder diffraction data); Nd(Pd_0.464(1)Ge_0.536(1))₂, KHg₂ structure type, space group Imma, a=4.469(2) Å, b=7.214(2) Å, c=7.651(3) Å, R₁=0.0402 for 189 reflections with F_o>4σ(F_o) (X-ray single crystal diffraction data); Eu(Pd,Ge)₂, AlB₂ structure type, space group P6/mmm, a=4.311(2) Å, c=4.235(2) Å; EuPdGe, EuNiGe structure type, space group P2₁/c, and ternary compound with unknown structure (X-ray powder diffraction data).     

High-pressure synthesis and crystal structures of two new polyphosphides, NaP5 and CeP5

Two novel polyphosphides, NaP₅ and CeP₅, were prepared in a BN crucible by the reaction of elemental components under a high pressure of 3 GPa at 800–950 °C. The X-ray structural analysis showed that NaP₅ crystallizes in an orthorhombic space group Pnma with a=10.993(2) Å, b=6.524(1) Å, c=6.903(1) Å, Z=4 and CeP₅ in the monoclinic group P2₁/m with a=4.9143(5) Å, b=9.6226(8) Å, c=5.5152(4) Å, β=104.303(6)°, Z=2. The crystal structure of NaP₅ consists of a three-dimensional framework _∞³[P₅]¹⁻ constructed by P---P bonds among four crystallographically inequivalent phosphorus sites, with large channels hosting the sodium cations, while CeP₅ is a layered compound containing _∞²[P₅]³⁻ polyanionic layers that are separated by Ce³⁺ ions. NaP₅ exhibits the diamagnetic behavior, while the temperature-dependent magnetic susceptibility of CeP₅ essentially follows the Curie–Weiss law.     

The crystal structure and magnetic properties of the Gd6Cr4Al43 compound

The crystal structure of intermetallic compound Gd₆Cr₄Al₄₃ has been investigated by means of X-ray diffraction data (Ho₆Mo₄Al₄₃ structure type, space group P6₃/mcm, Pearson symbol hP106, a = 10.9144(7) Å, c = 17.7361(13) Å).

SQUID magnetic measurements carried out for the title compound point to the existence of two antiferromagnetic phase transitions observed at T_N1 = 19.0(1) K and T_N2 = 6.8(1) K, respectively.     

LaMg2NiH7, a novel quaternary metal hydride containing tetrahedral [NiH4] complexes and hydride anions

A new ternary compound of composition LaMg₂Ni has been found and investigated with respect to structure and hydrogenation properties. It crystallizes with the orthorhombic MgAl₂Cu type structure (space group Cmcm, a=4.2266(6), b=10.303(1), c=8.360(1) Å; V=364.0(1) ų; Z=4) and absorbs hydrogen near ambient conditions (<200 °C, <8 bar) thereby forming the quaternary metal hydride LaMg₂NiH₇. Neutron powder diffraction on the deuteride revealed a monoclinic distorted metal atom substructure (LaMg₂NiD₇: space group P2₁/c, a=13.9789(7), b=4.7026(2), c=16.0251(8) Å; β=125.240(3)°, V=860.39(8) ų; Z=8) that contains two symmetry independent tetrahedral [NiD₄]⁴⁻ complexes with Ni–D bond lengths in the range 1.49–1.64 Å, and six D⁻anions in tetrahedral metal configuration with bond distances in the ranges 1.82–2.65 Å (Mg) and 2.33–2.59 Å (La). The compound constitutes a link between metallic ‘interstitial’ hydrides and non-metallic ‘complex’ metal hydrides.     

The molybdenum diphosphate Mo1.3O(P2O7), containing Mo2 and Mo3 clusters

A novel molybdenum diphosphate, Mo_1.3O(P₂O₇), was obtained by electrochemical lithium deintercalation. The diphosphate crystallises in space group I2/a with the lattice parameters a=22.88(1), b=22.94(2), c=4.832(1) Å, γ=90.36°, Z=8. Its original framework is built up from MoO₆ octahedra, P₂O₇ groups and also from MoO₄, Mo₂O₄ and Mo₃O₈ units containing Mo₂ and Mo₃ clusters. These polyhedra delimit large octagonal and z-shaped tunnels running along c, in which the inserted cations may be located.     

Power factor of La1−xSrxFeO3 and LaFe1−yNiyO3

The electrical conductivity (σ), Seebeck coefficient (S), and power factor (σS²) of perovskite-type LaFeO₃, La_1−xSr_xFeO₃ [0.1 ≤ x ≤ 0.4] and LaFe_1−yNi_yO₃ [0.1 ≤ y ≤ 0.6] were investigated in the temperature range of 300–1100 K to explore their possibility as thermoelectric materials. The electrical conductivity of LaFeO₃ showed semiconducting behavior, and its Seebeck coefficient changed from positive to negative around 650 K with increasing temperature. The electrical conductivity of LaFeO₃ increased with the substitutions of Sr and Ni atoms, while its Seebeck coefficient decreased. The Seebeck coefficient of La_1−xSr_xFeO₃ was positive, whereas that of LaFe_1−yNi_yO₃ changed from positive to negative with increasing Ni content. The substitutions of Sr and Ni were effective in increasing the power factor of LaFeO₃; 0.0053 × 10⁻⁴ Wm⁻¹ K⁻² for LaFeO₃ (1050 K), 1.1 × 10⁻⁴ Wm⁻¹ K⁻² for La_1−xSr_xFeO₃ (x = 0.1 at 1100 K) and 0.63 × 10⁻⁴ Wm⁻¹ K⁻² for LaFe_1−yNi_yO₃ (y = 0.1 at 1100 K).     

Synthesis, structure and fluorescence properties of a highly stable indium(III)-2,5-pyridinedicarboxylate coordination polymer

The hydrothermal reaction of 2,5-pyridinedicarboxylic acid (H₂PDC), diethylene triamine and In(NO₃)₃·4.5H₂O gave rise to a two-dimensional (2D) coordination polymer In(OH)(2,5-PDC). This compound crystallizes in the orthorhombic space group Iba2, with cell parameters, a = 12.656(3) Å, b = 20.114(4) Å, c = 6.2216(1) Å, V = 1583.9(5) Å³ and Z = 8. Its structure contains one-dimensional In–O–In–O– chains, which are further linked by 2,5-PDC ligands into a 2D supramolecular neutral framework. The adjacent 2D layers are parallel with each other and construct a three-dimensional framework via hydrogen bands. At room temperature, the compound exhibits intense photoluminescence. On the basis of the results of TG/DTA analyses, the structure is thermally stable up to 390 °C.