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 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.     

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 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.     

Über Perowskitphasen des Systems Ba2Y0,67U1−xWxO6

On Perovskite Phases of the System Ba₂Y_0,67U_1?xW_xO₆ A solid solution series is formed between the polymorphic perovskites Ba₂Y_0.67UO₆ and Ba₂Y_0.67WO₆ (cubic: a = 8.37₂ Å; hexagonal: a = 4× 5.88₁ Å and c = 4× 7.77₈ Å). The structure is cubic between x = 0.1 and 0.99 and for x > 0.95 hexagonal as well. Strong deviations from the ideal behaviour are detectabel with spectroscopic methods. The shape of the UO₆ and WO₆ octahedrons experiences only minor changes within the series.     

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.     

Über hexagonale Perowskite mit Kationenfehlstellen. XXVII. Die Systeme Ba4−xSrxBIIRe2□O12′, Ba4BCaxRe2□O12 und Ba4−xLaxBIIRe2−xWx□O12 mit BII = Co,Ni

On Hexagonal Perovskites with Cationic Vacancies. XXVII. Systems Ba_4?xSr_xB^IIRe₂□O₁₂, Ba₄B Ca_xRe₂□O₁₂, and Ba_4?xLa_xB^IIRe_2?xW_x□O₁₂ with B^II = Co, Ni In the systems Ba_4?xSr_xB^IIRe₂□O₁₂, Ba₄BCa_xRe₂□O₁₂ and Ba_4?xLa_xB^IIRe_2?xW_x□O₁₂ (B^II = Co, Ni) hexagonal perovskites with a rhombohedral 12 L structure (general composition A₄BM₂□O₁₂; sequence (hhcc)₃; space group R&3macr;m) are observed. With the exception of Ba₄NiRe₂□O₁₂ the octahedral net consists of BO₆ single octahedra and M₂□O₁₂ face connected blocks (type 1). In type 2 (Ba₄NiRe₂□O₁₂) the M ions are located in the single octahedra and in the center of the groups of three face connected octahedra. The two outer positions of the latter are occupied by B ions and vacancies in the ratio 1:1. The difference between type 1 and 2 are discussed by means of the vibrational and diffuse reflectance spectra.     

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 hexagonale Perowskite mit Kationenfehlstellen. XXXIII. Verbindungen vom Typ Ba6−xSrxB2−y3+SEy3+W3□O18

On Hexagonal Perovskites with Cationic Vacancies. XXXIII. Compounds of Type Ba_6?xSr_xB_2?y³⁺SE_y³⁺W₃□O₁₈ In the series Ba_6?xSr_xLu_2?ySE_y³⁺W₃□O₁₈ a substitution of Sr²⁺ for Ba²⁺ is possible. According to intensity calculations on powder data of BaSr₅Lu_1,6Ho_0,4W₃□O₁₈ the compounds crystallize in a rhombohedral 18 L type with the sequence (hhcccc)₃; space group R3 m. The refined, intensity related R' value is 11.5%. The differences in properties (diffuse reflectance spectra, photoluminescence) between the hexagonal modifications Ba₆B_2?y³⁺SE_y³⁺W₃□O₁₈ (B³⁺ ? Gd, Y, Lu; SE³⁺ ? Sm, Eu, Tb, Dy, Ho, Er, Tm) and the corresponding cubic HT modifications are discussed.     

Photolumineszenz im System A2II B1/4II Gd1/2−x Eux □1/4 WO6 ≙ A8II BII Gd2−x Eux □ W4O24 (AII,BII = Sr,Ba)

Photoluminescence in the System A₂^II B_1/4^IIGd_1/2?xEu_x□_1/4WO₆ ? A₈^IIB^IIGd_2?xEu_xW₄O₂₄ (A^II, B^II = Sr, Ba) The emission and excitation spectra for the series Sr₈SrGd_2?xEu_x□W₄O₂₄ (HT- and LT-modifications) and Sr_9?yBa_yEu₂□W₄O₂₄ are reported and discussed. HT- and LT-Sr₈SrEu₂□W₄O₂₄ show an intense red emission, no concentration quenching is present.     

Die Photolumineszenz der dreiwertigen Seltenen Erden in den Perowskitstapelvarianten Ba2La2−xSE MgW2□O12, Ba6Y2−xSEW3□O18 und Sr8SrGd2−x SEW4□O24

Photoluminescence of Trivalent Rare Earths in Perovskite Stacking Polytypes Ba₂La_2?x RE MgW₂□O₁₂, Ba₆Y_2?x RE W₃□O₁₈, and Sr₈SrGd_2?xRE W₄□O₂₄ Rhombohedral 12 L stacking polytypes Ba₂La_2?xREMgW₂□O₁₂ show with RE³⁺ = Pr, Sm, Eu, Tb, Dy, Ho, Er, Tm; the 18 L stacking polytypes Ba₆Y_2?xREW₃□O₁₈ and the polymorphic perovskites Sr₈SrGd_2?xREW₄□O₂₄ with RE³⁺ = Sm, Eu, Dy, Ho, Er visible photoluminescence. The concentration dependence and the influence of the coordination number of the rare earth are reported.     

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.     

Über den Einfluß von A und B auf die Bindungsverhältnisse in geordneten Perowskiten A2BB′O6. Die Systeme Ba2−xSrxCdUO6 und Ba2−xSrxZnUO6

On the Influence of A and B on the Bonding in Ordered Perovskites A₂BB′O₆. The Systems Ba_2?xSr_xCdUO₆ and Ba_2?xSr_xZnUO₆ In the systems Ba_2?xSr_xBUO₆ for B = Cd a complete substitution of Ba²⁺ by Sr²⁺ is observed, whereas with B = Zn the phase boundary is near x ? 1.25. By measurement of charge transfer and vibrational spectra the influence of the A and B nature on the properties is shown. By comparison with the corresponding Mg- and Ca-perovskites the influence of the electronic configuration (d⁰ or d¹⁰) is studied as well.     

Luminescence and vibrational spectra of Ba5Li2W3O15

The infrared and Raman spectra of Ba₅Li₂W₃O₁₅ are reported down to 200 cm^?1. From the internal stretching modes of the tungstate octahedra the crystallographic order between lithium and tungsten in the face-sharing octahedra can be derived. The green tungstate luminescence shows a low quenching temperature that is described with the Dexter-Klick-Russell model. The U⁶⁺ ion shows a yellow emission in Ba₅Li₂W₃O₁₅. There is ample evidence for two different U⁶⁺ centers with different decay times (10 and 80 μsec) and different emission and excitation spectra. One of these is located in a single layer of tungstate octahedra, the other in a double layer of octahedra.     

Synthese und Strukturuntersuchungen von Ba2H[α-FeO4W12O36] · 26 H2O

Synthesis and Structure Studies of Ba₂H[α-FeO₄W₁₂O₃₆] · 26 H₂O The heteropolyanion compound Ba₂H[α-FeO₄W₁₂O₃₆] · 26 H₂O (I) crystallizes in the tetragonal space group P4 n2 with the lattice parameters a = 12.398(6), c = 18.721(6) Å; Z = 2; D_x = 4.128 g · cm^?3. The structure was solved on a twinned crystal from 1029 observed reflections and refined to an index R of 7.6%. The calculations were done by means of a modified ORFLS-programme by Eitel and Bärnighausen. The heteropolyanion [α-FeO₄W₁₂O₃₆]^5? has the well known α-Keggin structure. The average distance of the four central oxygen atoms to the Fe^III position (0, 0, 0) is 1.84 Å. The angles ? O? Fe? O are 112.3° (4X) and 103.9 (2X), respectively, which leads to an disphenoidal distortion of the FeO₄ tetrahedron. The powder and single crystal ESR spectra of I show the anisotropy of the Fe^III fine structure transition 1/2 ? ?1/2. The Mößbauer spectra confirm the tetragonal distortion of the central FeO₄ tetrahedron (quadrupole splitting Δ ≈ 0.50 mm · s^?1).     

Über Verbindungen vom Typ Ba3BIIMO9 mit BII  Mg,Ca, Sr,Ba und MV  Nb,Ta

Compounds of the Type Ba₃B^IIM O₉ with B^II ? Mg, Ca, Sr, Ba, and M^V ? Nb, Ta The hexagonal perovskites Ba₃B^IIMO₉ (M^V ? Nb, Ta) crystallize with B^II ? Mg Ca in a 3 L structure (sequence (c)₃) and B^II ?; Sr in the hexagonal BaTiO₃ type (6 L; sequence (hcc)₂) with an 1:2 order for the B and M ions. Intensity calculations for Ba₃SrNb₂O₉ and Ba₃SrTa₂O₉ gave in the space group P6₃/mmc a refined, intensity related R′ value of 8.4% (Nb) and 9.0% (Ta) respectively. For B^II ? Ba the perovskite Ba₃BaTa₂O₉ has an orthorhombic distorted 6 L structure and forms with Ba₃SrTa₂O₉ a continuous series of mixed crystals (Ba₃Sr_1?xBa_xTa₂O₉). In the system Ba₃Sr_1?xBa_xNb₂O₉ the range of existence of the hexagonal BaTiO₃ type is confined to the Sr richer end. The pure Ba compound possesses a proper structure type (5 L: Ba₅BaNb₃□O_13.5□_1.5).     

Hydration and proton transport in solid solutions based on Ba<Subscript>2</Subscript>CaWO<Subscript>6</Subscript>

Hydrated alkaline-earth metal tungstates Ba₄Ca_{2 + x} W_{2 ? x} O_{12 ? 2x} with perovskite structure were studied by the thermogravimetry, ¹H NMR, IR, and Raman spectroscopy methods. Electrical conductivity and transfer numbers were measured with varying T, \(p_{O_2 } \) and \(p_{H_2 O} \). The solid solutions are capable of reversibly intercalating water and can exhibit high-temperature proton transport. The localization of protons on oxygen results in the appearance of energetically nonequivalent OH groups; a small fraction of protons are present in the form of H₂O and H₃O⁺.     

Spectroscopic investigation of La7Ta3W4O30:Sm3+ orange-red phosphor for white LEDs

The novel orange-red light emitting La₇Ta₃W₄O₃₀:xSm³⁺ (x = 0.005–0.20) phosphors were synthesized via the solid-state reaction method. The crystal structure, photoluminescence (PL) properties, optimum concentration, color purity, decay life, and thermal stability of the samples were systematically studied. Under the excitation of 404 nm, La₇Ta₃W₄O₃₀:Sm³⁺ emits intense orange-red light at 597 nm. The PL spectra of La₇Ta₃W₄O₃₀:Sm³⁺ phosphors are ascribed to the ⁴G_5/2 to ⁶H_J (J = 5/2, 7/2, 9/2, and 11/2) transitions of Sm³⁺ ions. The concentration quenching occurs at the doping level of 1 mol%. The quenching temperature is higher than 500 K. Finally, a white LED (w-LED) with the Commission Internationale de L'Eclairage (CIE) chromaticity coordinates of (0.312, 0.296) and good color rendering index (Ra) of 86 was fabricated. As a consequence, all the results suggest that the orange-red phosphors La₇Ta₃W₄O₃₀:Sm³⁺ have potential applications in w-LEDs structures.     

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.