Über die Polymorphie der Perowskite Ba2SE0,67WVIO6. II. Die Systeme Ba2Nd0,67(1−x) Y0,67xWO6 und Ba2Nd0,67W1−xUxO6

Polymorphism of Perovskite Compounds Ba₂SE_0.67W^VIO₆. II. The Systems Ba₂Nd_0.67(1?x)Y_0.67xWO₆ and Ba₂Nd_0.67W_1?xU_xO₆ In the system Ba₂Nd_0.67(1?x)Y_0.67xWO₆ the formation of a continuous series of mixed crystals with cubic 1:1 ordered perovskite structure is observed. The existence of a hexagonal modification is confined to the Y-rich side (x ≥ 0,9). In the Ba₂Nd_0.67W_1?xU_xO₆ series only for x ? 0,25 homogeneous cubic perovskites are obtained. In contrast to systems with other rare earths the Nd series show uncommon optical properties.     

Gibt es „Wolframylgruppierungen”︁? Über Perowskitphasen im System Ba2Y0,67UO6?Ba2CaWO6

Do ? Wolframyl Groups ”? Exist? On Perovskite Phases in the System Ba₂Y_0,67UO₆ ? Ba₂CaWO₆ In the system Ba₂Y_{0.67(1? x)}Ca_xU_{1? x}W_xO₆ a solid solution series is formed up to x ? 0.85. The properties are studied by x-ray and spectroscopic methods.     

Über Das System Ba2Sm0,67U1−xWxO6

On the System Ba₂Sm _0.67U_1?xW_xO₆ The ordered perovskites Ba₂Sm_0.67UO₆ and Ba₂Sm_0.67 WO₆ are forming a complete serie of solid solutions with 4 formula units Ba₂Sm_0.67U_1?xW_xO₆ in the unit cell. By diffuse reflectance and i.r.-spectroscopic measurements the relations between color and constitution are shown.     

Über Neue Oxoruthenate vom Typ der 6 L-Perowskite: Ba3SrRu2−xTaxO9 (x = 0,8 und 1,4) mit einem Beitrag über Ba3CaRu2O9

On Novel Oxoruthenates of the 6 L-Perovskite Type: Ba₃SrRu_2?xTa_xO₉ (x = 0.8 and 1.4) with a Comment on Ba₃CaRu₂O₉ Single crystals of the phases Ba₃SrRu_2?xTa_xO₉ [(I): x = 0.8 and (II): x = 1.4] and the compound (III): Ba₃CaRu₂O₉ were prepared by a BaCl₂ flux and investigated by X-ray methods. (I)–(III) crystallizes with hexagonal symmetry space group P6 2c with lattice constants: (I) a = 6.003 Å; c = 15.227 Å; (II) a = 5.988 Å; c = 15.220 Å and (III) a = 5.891 Å; c = 14.571 Å. The crystal structures of these substances corresponds to the 6 layer perovskites with the stacking sequence (hcc)₂. All of them show a so far not described slightly distorted oxygen framework caused by the Sr²⁺ and Ca²⁺ ions.     

Über die Polymorphie der Wolframperowskite Ba2SE0,67WO6

Polymorphism of Tungsten Perovskite Compounds Ba₂SE_0,67WO₆ The compounds Ba₂SE_0,67WO₆ with SE = Gd? Lu are polymorphic. Above 1200°C the instable cubic modification (ordered perovskit with 4 formula units Ba₂SE_0,67□_0,33WO₆ per cell) transforms irreversibly into a hexagonal modification with completely filled cationic lattice. For Ba₂Eu_0,67WO₆ the transformation is incomplete. With SE = Nd and Sm only the cubic modification is formed.     

Über die Eigenschaftsänderungen beim Einbau von Tav in Ba2Gd0,67UO6

The Variation of Properties by Incorporation of Ta^v in Ba₂Gd_0.67UO₆ In Ba₂Gd□_0.33U^VIO₆ the complete substitution of U^VI by Ta^V is only possible by filling up the gadolinium vacancies (Ba₂Gd_0.67+0.33xU_1?xTa_xO₆), whereas in the series Ba₂Gd_0.67U_1?yTa_yO_6–0.5y the phase boundary is reached with y = 0.1. Depending on x the variation of the properties is studied by X-ray and spectroscopic methods.     

Über das System Ba2Sm0,67(1-x)La0,67xUO6

On the System Ba₂Sm_0.67(1?x)La_0.67xUO₆ In the Ba₂Sm_0.67xUO₆ system the boundary of the perovskite phase reachs up to x ? 0.33. With increasing Lanthanum content a transition from a structure with vacancies in the SE³⁺-sublattice to a lattice typ with interstitial oxygen is observed. By the interpretation of the reflectance and vibrational spectra the relations between colour and constitution are shown.     

Structural chemistry of Sr3Cr2WO9, Ca3Cr2WO9, and Ba3Cr2WO9

We have studied the preparation and crystallographic structure of three perovskite-type compounds: Sr₃Cr₂WO₉, cubic, the lattice parameter of which is a = 7.812Å; Ca₃Cr₂WO₉, tetragonal, the lattice parameters of which are a = 5.408 Å and c = 7.635Å; and Ba₃Cr₂WO₉, hexagonal, the lattice parameters of which are a = 5.691 Å and c = 13.957Å. We have compared these three structures and shown the relationship between the dimensions of the alkaline-earth metal and the existence of the different structures.     

Beiträge zur Chemie der Halogensilan-Addukte. XII. 1,10-Phenanthrolin-N-Oxid-Komplexe von Halogensilanen

On Perovskite Phases in the Systems AO? SE₂O₃? UO_2,x with A =Alkaline Earth Metal and SE = Rare Earths, La and Y. X. The Systems Ba₂CaUO₆? Ba₂CaUO₆? Ba₂Lu_0.67UO₆ and Ba₂SrUO₆? Ba₂Lu_0.67UO₆ In the systems Ba₂B_1?xLu_0,67x UO₆ with B^II = Ca, Sr at the B-rich side rhombic and at the Lu-rich side monoclinic perovskites are formed. The transition is discontinuous and accompanied by order-disorder phenomena.     

Über Das System Ba2Gd2/3□1/3U1−xWxO6 sowie hexagonale Perowskite vom 18-

On the System Ba₂Gd_2/3□_1/3U_1?xW_xO₆ and Hexagonal Perovskites of an 18-Layer Type In the system Ba₂Gd_2/3□_1/3U_1?xW_xO₆ the formation of a continuous solid solution series is observed. With x ? 0.9 the mixed crystals have a cubic 1:1 ordered perovskite structure. With x ≥ 0.95 the compounds are polymorphic: besides an cubic 1:1 ordered perovskite type for x = 0.95; 0.99 and 1.00 one hexagonal layer structure exists. This lattice is in all cases rhombohedral (space group R3 m) and represents an 18 L-type. Likewise the compounds Ba₂B□_1/3W^VIO₆ with B^III = Tb-Lu and Y belong to the 18 L-type.     

Darstellung und Kristallstruktur der Phasen Li26Na58Ba38Ex (E = N,H; x = 0 – 1)

Preparation and Crystal Structures of Li₂₆Na₅₈Ba₃₈E_x Phases (E = N, H; x = 0 – 1) Li₂₆Na₅₈Ba₃₈E_x (E = N, H; x = 0–1) were prepared as a majority phase by the reactions of the metals with Ba(N₃)₂ or BaH₂ at 250 °C for five days. According to single crystal and powder X‐ray diffraction investigation, all compounds are cubic, space group with the unit cell parameter a ranging from 27.335(2) (x = 0) to 27.554(3) (x = 1, E = N, H) Å and Z = 4. This compound series can be described as a filled variant of Li₁₃Na₂₉Ba₁₉, in which nitrogen or hydrogen atoms are found in the centre of Li₂₆ clusters in tetrahedral environment. Li₂₆Na₅₈Ba₃₈E_x represents a new group of metal‐rich compounds extending the growing family of subnitrides.     

Ein neues Mangan(II)-Oxowolframat: Mn3WO6

On a New Manganese(II) Oxotungstate: Mn₃WO₆ Single crystals of Mn₃WO₆ were prepared by CO₂-LASER technique in H₂-atmosphere and investigated by single crystal X-ray work. It crystallizes with rhombohedral symmetry, space group C? R3 with the hexagonal lattice constants a = 8.8931 Å; c = 10.4782 Å and Z = 6. Mn₃WO₆ is isotypic to Mg₃TeO₆ and α-Ca₃UO₆ and characterized by to each other isolated WO₆ octahedra. The surrounding of them by six inner-sphere and six outer-sphere MnO₆ polyhedra is discussed.     

Über Geordnete Perowskite mit Kationenfehlstellen. II. Der Ersatz von UVI durch NbV in Ba2Gd0,67□0,33UO6

On Ordered Perovskites with Cationic Vacancies. II. The Incorporation of Nb^V in Ba₂Gd_0,67□_0,33UO₆ In Ba₂Gd_0.67□_0.33UO₆ a complete substitution of U^VI by Nb^V is possible by filling the cationic vacancies (x-phase: Ba₂Gd_0.67+0.33xU_1?xNb_xO₆). For the y-Phase (Ba₂Gd_0.67U_1?yNb_yO_6?0.5y) solid solutions are formed only for y ? 0.5. The properties of both phases are studied by x-ray and spectroscopic methods. In Ba₂GdNbO₆ – in contrary to the complete ordered Ba₂GdTaO₆ – the order of gadolinium and niobium id partial.     

Ba0.15WO3: A bronze with an original pentagonal tunnel structure

The structure of a new barium tungsten bronze, Ba_0.15WO₃, has been established by X-ray diffraction and high-resolution microscopy studies. This bronze is orthorhombic, space group Pbm2 or Pbmm, with a = 8.859(3) Å, b = 10.039(8) Å, and c = 3.808(2)Å. The “WO₃” framework is built up from corner-sharing WO₆ octahedra forming pentagonal tunnels where the barium ions are located. Structural relationships with hexagonal tungsten bronze and tetragonal tungsten bronze structures are discussed.     

Über das System Ba2Zn1−xCuxUO6 — ein schwingungsspektroskopischer Nachweis des Jahn-Teller-Effekts

On the System Ba₂Zn_1?xCu_xUO₆. A Vibrational Spectroscopic Proof of the Jahn Teller Effect The ordered perovskites Ba₂ZnUO₆ (cubic, space group Fm3m) and Ba₂CuUO₆ (tetragonal, space group I₄/mmm) form solid solutions. For small Cu content the lattice symmetry is cubic, with x ≥ 0.25 an increasing tetragonal distortion (c/a √2 > 1) is observed. From the vibrational spectra and in accordance with the factor group analysis the symmetry of the UO₆ octahedra is for small Cu content O_h and on the Cu-rich side D_4h. In the region of the lattice vibrations (T₂ field) the lifting of the degeneracy — due to the Jahn Teller effect of Cu²⁺ — leads to a band separation, which decreases with sinking copper content. Therefore the Jahn Teller effect is easily noticeable with vibrational spectroscopic methods. In the corresponding series with W^VI the vibrational spectroscopic investigations lead qualitatively to the same results as in the U^VI system. As further examples the stacking polytypes Ba₂ZnTeO₆ and Ba₂CuTeO₆ are considered. The vibrational spectra show, that the Jahn Teller effect in this lattice, which is strengthened by partial face-sharing of octahedra, is less pronounced than in the perovskites in which only corner-sharing is present.     

Perovskite solid solutions in the BaO-CuO-Y2O3-Nb2O5 system

Freeze dried complex carboxylates are highly reactive precursors for complex perovskite solid solutions in the system BaO-CuO-Y₂O₃-Nb₂O₅ On thermal decomposition of the amorphous precursors the formation of complex crystalline phases begins at 600 °C. In most cases the themodynamically controlled phase composition is reached after a reaction time of two hours at about 900 °C. Beginning from the perovskite compound Ba₂YNbO₆ a partial substitution of Y by Cu or by a combination 2/3 Cu,1/3 Nb leads to extended fields of solid solutions with cubic perovskite structure. Substitution according to Y_0,5xBa₂(Y_1-0,5xCu_xNb)O_6+x is limited to x ≤ 0,4. A compound LBa₂Cu₂NbO₈ (x=2), well characterized for L=La, does not exist for L=Y. The composition of solid solutions depends on the preparation conditions. There are some signs for an inhomogeneous distribution of B-cations in the cubic perovskites.     

Spektroskopische und strukturelle Untersuchungen an hexagonalen Elpasolithen

Inhaltsübersicht. Es werden die Ergebnisse der röntgenographischen, ligandenfeldspektro-skopischen sowie IR-spektroskopischen Untersuchungen des Mischkristallsystems Sr_2–xBa_xNi TeO₆ mitgeteilt und mit denen entsprechender Untersuchungen der Mischkristalle Ba₂NiTe_xW_1–xO₆ und Ba₂Ni_xMg_1–xTeO₆ verglichen. In diesen Systemen ist mit wachsendem x ein Übergang von der Elpasolith- über die hexagonale BaTiO₃-(6-Schichten-) zur hexagonalen Ba₂NiTeO₆-(12-Schichten-) Struktur zu beobachten. Im Falle der Verbindungen Sr_2–xBa_xNiTeO₆ konnten zusätzlich bei kleinen x-Werten Übergänge von der monoklinen Struktur (Sr₂NiTeO₆) über eine tetragonale Variante der Elpasolithstruktur zum kubischen Gitter gefunden werden. Mittels bei 4 K und 293 K aufgenommener Ligandenfeldspektren wird die Auswirkung der strukturellen Veränderungen beim Ubergang von der geordneten Elpasolithstruktur zu den hexagonalen Varianten auf die Symmetrie und die Bindungsverhältnisse der NiO₆-Oktaeder verfolgt, während die IR-Spektren zusätzlich die Symmetrieverände-rungen der TeO₆-Oktaeder erkennen lassen. Schließlich konnte mit Hilfe beider spektroskopischen Methoden Aussagen über die Kationenverteilung in den hexagonalen Phasen gemacht werden. Spectroscopic and Structural Investigations on Hexagonal Elpasolites The results of X-ray as well as ligand field and i.r. spectroscopic investigations of the mixed crystal series Sr_2–xBa_xNiTeO₆ are reported and compared with those of Ba₂NiTe_xW_1–xO₆ and Ba₂Ni_xMg_1–xTeO₆. In these compounds transitions from the elpasolite to the hexagonal BaTiO₆ (6 layers) and finally to the hexagonal Ba₂NiTeO₆ (12 layers) structure are observed with increasing x. In addition a change from the monoclinic structure (Sr₂NiTeO₆ type) to a tetragonal variant of the elpasolite lattice and finally to the cubic structure is found in the mixed crystal series Sr_2–xBa_xNiTeO₆ at low x values. The influence of these structural changes on the symmetry and the bonding within the NiO₆ polyhedra is studied by the parameters taken from the 4 K and 293 K ligand field spectra. In addition the i.r. spectra give information with respect to the symmetry of the TeO₆ polyhedra. Finally the cation distribution in the hexagonal phases could be deduced from the spectroscopic data.     

Ba7Fe6F32 · 2H2O: Original isolated trimers [Fe3F16]7− in a new defective jarlite-type compound

Ba₇Fe₆F₃₂ · 2H₂O was prepared from HF aqueous solution in a teflon bomb (Berghof) at 180°C. A partial exchange F^?/OH^? can be realized in more diluted HF medium and leads to Ba₇Fe₆F_32–x(OH)_x · 2H₂O. The compounds crystallize in the monoclinic system, space group C2/m (Z = 2) with a = 17.023(1) Å, b = 11.482(1) Å, c = 7.624(1) Å, β = 101.13(1)° for x = 0 and a = 17.036(2) Å, b = 11.489(1) Å, c = 7.620(2) Å, β = 101.48(1)° for x ≈? 5.3. The structures were determined from 2 256 and 1 343 independent reflections for x = 0 and x ≈? 5.3 respectively, collected with a Siemens AED2 four-circle diffractometer with the MoKα radiation (R = 0.0235 and R_w = 0.0240 for x = 0 and R = 0.0324 and R_w = 0.0335 for x ≈? 5.3). The structure, closely related to that of the Jarlite-type, is built up from isolated octahedra trimers [Fe₃F₁₆]^7?, connected together by Ba²⁺-cations. The location of anions and water molecules is discussed from bond valence calculations. Magnetic and Mössbauer studies are reported and discussed.     

Über Ba2Ce0,75SbO6 – den ersten Vertreter einer weiteren Perowskitvariante

On Ba₂Ce_0,75SbO₆ – the First Representant of a Further Perovskite Variant The ochre coloured Ba₂Ce_0,75SbO₆ represents a perovskite variant with vacancies in the cationic lattice. The tetragonal cell dimensions are: a = 2×5,97₇ Å and c = 2×8,50₀ Å.     

The h-SbxWO3+2x Oxygen Excess Antimony Tungsten Bronze

We describe the previously unreported oxygen excess hexagonal antimony tungsten bronze with composition Sb_0.5W₃O₁₀, in the following denoted as h-Sb_xWO_3+2x with x=0.167, to demonstrate its analogy to classical A_xWO₃ tungsten bronzes. This compound forms in a relatively narrow temperature range between 580 °C<T<620 °C. It was obtained as a dark-blue polycrystalline powder, and as thin, needle-shaped, blue single crystals. h-Sb_xWO_3+2x crystallizes in the hexagonal space group P6/mmm with the cell parameters a=7.4369(4) Å and c=3.7800(2) Å. The antimony and excess oxygen occupy the hexagonal channels within the network of corner-sharing WO₆ octahedra. h-Sb_xWO_3+2x has a resistivity of ρ_{300 K}≈1.28 mΩ cm at room temperature, with little if any temperature-dependence on cooling. DFT calculations on a simplified model for this compound find a metallic-like electronic structure with the Fermi level falling within rather flat bands, especially around the Γ point.