Die Kristallstrukturen der hexagonalen Elpasolithe Ba3NiSb2O9 und Ba3CuSb2O9 – röntgenographische und spektroskopische Ergebnisse

The Structures of the Hexagonal Elpasolite-Type Compounds Ba₃NiSb₂O₉ and Ba₃CuSb₂O₉ The results of an X-ray single crystal study of the hexagonal elpasolite Ba(NiSb₂)⁽⁶⁾O₉ are given. (Space group: C; a = b = 5.837 Å, c = 14.392 Å; Z = 2). The structure can be described by close-packed BaO₃ layers alternating in the sequence c c h c c h … (hex. BaTiO₃ type). Groups of two octahedra with common faces are connected by SbO₆ octahedra via common corners. They are occupied alternately by Ni and Sb. The final reliability index was R = 3.0%. The Cu²⁺-compound is of the same structural type. The ligand field and EPR spectra are discussed in comparison with related Ni²⁺ and Cu²⁺ compounds.     

Die Kristallstruktur von Perowskiten ANiIIMVIO6. II. Das Sr2NiWO6

The Crystal Structure of Perovskites A Ni^IIM^VIO₆. II. Sr₂NiWO₆ The results of an X-ray single crystal study of the perovskite Sr[Ni^IIW^VI]⁽⁶⁾O₆, ordered in the octahedral sites, are given. While Sr[Ni^IITe^VI]⁽⁶⁾O₆ crystallizes in a monoclinically deformed structure of the perovskite (elpasolite) type, showing a phase transition to a tetragonal lattice at 675 °K, Sr[Ni^IIW^VI]⁽⁶⁾O₆ is tetragonal already at 298°K (space group: C; a = b = 5.559 Å; c = 7.918 Å; Z = 2). The Ni? O distances found for the tungsten compound are nearly identical with those of the tellurium perovskite. In contradiction to crystal field theory very different values of the ligand field parameter Δ (ca. 25%) are observed for these two compounds however. Obviously this effect is caused by the rather different kind of bonding within the NiO₆ polyhedra in the two compounds. On the basis of the structural results the Ni? O-bonding in the two perovskites is discussed in dependence of the next nearest cationic environment.     

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.     

Ba3Lu4O9: Synthese und Strukturuntersuchung

Ba₃Lu₄O₉: Synthesis and Crystal Structure Determination Single crystals of Ba₃Lu₄O₉ were prepared by high temperature reactions (CO₂-Lasertechnique). The single crystal X-ray work leads to a rhombohedral symmetry with a = 8.96 Å and α = 39.42° (space group C—R3). Characteristic features of this crystal structure are shown and discussed.     

Ba6CoNb9O30: Ein neuer Vertreter der tetragonalen Wolframbronzen

Ba₆CoNb₉O₃₀: A New Compound of the Tetragonal Bronze Structure The hitherto unknown compound Ba₆CoNb₉O₃₀ was examined by X-ray single crystal work. (Space group C-P4bm; a = 1258.9; c = 400.9 pm) Co³⁺ and Nb⁵⁺ occupy a special position in an octahedral framework. The coordination of Ba²⁺ is discussed.     

Über hexagonale Perowskite mit Kationenfehlstellen. XXVI. Ba12Ba2 2/3M 1/3□2O33□3 (MV = Nb,Ta) – die ersten Stapelvarianten eines rhomboedrischen 36 L-Typs

On Hexagonal Perovskites with Cationic Vacancies. XXVI. Ba₁₂Ba_{2 2/3}M _1/3□₂O₃₃□₃ (M^V = Nb, Ta) – the First Stacking Polytypes of a Rhombohedral 36 L-Type In the systems BaO? MO₅(M^V = Nb, Ta) for a Ba:M^V ratio of 2:1 polymorphism is observed. Here the low temperature modifications are described. They crystallize in a rhombohedral 36 L structure with three formula units Ba₁₂Ba_{2 2/3}M _1/3□₂O₃₃□₃ for the trigonal setting (M^V = Nb: a = 5.92₂ Å; c = 93.₂₅ Å; Ta: a = 5,92₂ Å; s = 93.4 Å).     

The Crystal Structure of Pb8FeIIFeF24: an ordered Fluorite-like Compound

Pb₈Fe^IIFeF₂₄ is triclinic: a = 20.118(3) Å, b = 5.597(1) Å, c = 9.440(2) Å, α = 89.75(2)°, β = 105.79(2)°, α = 89.38(2)°, Z = 2. The structure is solved in the unconventional space group C1 , from X-ray single crystal data using 1 641 independent reflections (R = 0.048, R_w = 0.051). It is built up from the stacking of two subnetworks along the a axis: fluorite-like [Pb₈F₁₀]_n⁶ⁿ⁺ layers and infinite dimetallic [Fe^IIFeF₁₄]_n^6n? double-chains of corner-sharing octahedra running along the b axis.     

Zur Kenntnis von Ba6La2Co4O15

About Ba₆La₂Co₄O₁₅ Ba₆La₂Co₄O₁₅ were prepared and investigated by X-ray single crystal work. It crystallizes with hexagonal symmetry, space group C–P6₃mc; a = 11.8082; c = 7.0019 Å; Z = 2. Ba²⁺ show face connected BaO₆-octahedra and larger polyhedra of C.N. = 10 and 12. Co³⁺ is surrounded by four and six (tetrahedra, octahedra) oxygen. The Ba²⁺ and La³⁺ ions occupy one point position statistically.     

Über hexagonale Perowskite mit Kationenfehlstellen. XVI Die rhomboedrischen 12 L-Stapelvarianten Ba3AIIIM□O12 mit MV = Nb,Ta

On Hexagonal Perovskites with Cationic Vacancies. XVI. Rhombohedral 12 L-Stacking Polytypes Ba₃A^IIIM □O₁₂ with M^V = Nb, Ta The white quaternary oxides Ba₃LaM□O₁₂ with M^V = Nb, Ta belong to the group of hexagonal perovskites with cationic vacancies. They crystallize in a rhombohedral 12 L-structure (sequence (hhcc)₃; space group R3 m) with a = 5.75₁ Å; c = 28.1₁ Å (M^V = Nb); a = 5.74₆ Å; c = 28.2₀ Å (Ta) and Z = 3. Signs for the formation of isotypic compounds with A^III = Pr, Nd could be obtained as well.     

Zur Kenntnis von Ba10Fe8Pt2Cl2O25

About Ba₁₀Fe₈Pt₂Cl₂O₂₅ The crystal structure of Ba₁₀Fe₈Pt₂Cl₂O₂₅ has been solved by direct methods, using intensity data collected by means of an automatic diffractometer (MoKα). It crystallizes in the hexagonal space group D–P6₃/mmc: a = 5.8034(4) Å, c = 24.997(5) Å, Z = 1. Fe³⁺ ions occur in both octahedral and tetrahedral coordination. Two types of Ba²⁺ ions are formed, with ten and twelve neighbouring atoms. The structure consists of plane connected FeO₆ and PtO₆ octahedra which are connected by corner shared FeO₄ tetrahedra.     

The crystal structure of Pb7FeIIFe6IIIF34: A new jarlite-type compound

Pb₇Fe^IIFeF₃₄ is monoclinic: a = 16.375(2) Å, b = 11.233(2) Å, c = 7.615(1) Å, β = 102.67(1)º, Z = 2. The crystal structure was solved in the space group C2/m (nº 12), from X-ray single crystal data using 957 independent reflections (705 with F/σ(F) > 4, leading to R = 0.038). It consists in infinite helicoidal [Fe^IIFeF₃₄]_n^14n? double-chains of cornersharing octahedra running along the b-axis and separated from each other by lead ions.     

Über hexagonale Perowskite mit Kationenfehlstellen. XXIV. Rhomboedrische 9 L-Stapelvarianten in den Systemen Ba3W M □ O9−x/2□x/2 mit MV = Nb,Ta

On Hexagonal Perovskites with Cationic Vacancies. XXIV. Rhombohedral 9 L Stacking Polytypes in the Systems Ba₃W M □O_9?x/2□_x?2 with M^V = Nb, Ta In the system Ba₃WNb□O_9?x/2□_x/2 stacking polytypes of rhombohedral 9 L type (sequence (hhc)₃; space group R3 m) can be prepared with ～1/3 ? × ? 2. For x = 2(Ba₃Nb₂□O₈□) two modifications are formed. In the corresponding Ta system the phase with is reduced to a smaller region with x ? 1/3.     

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).     

Über hexagonale Perowskite mit Kationenfehlstellen. XIV Die rhomboedrischen 12 L-Stapelvarianten Ba2La2BII(W□O12)

On Hexagonal Perovskites with Cationic Vacancies. XIV. The Rhombohedral 12 L-Stacking Polytypes Ba₂La₂B^II(W □O₁₂) Rhombohedral 12 L-stacking polytypes with cationic vacancies of type Ba₂La₂B^II-(W□O₁₂) are reported for B^II = Mg, Zn (white), Ni(light brown) and Co(brown). They crystallize in the space group R3 m, sequences (3 )(1) ? (hhcc)₃. For B^II = Cu, as a consequence of the Jahn Teller effect, a triclinic distorted lattice is observed.     

Über Erdalkalimetalloxothallate. II. Darstellung und Kristallstruktur von Ba2Tl2O5

On Alkaline Earth Metal Oxothallates. II. Preparation and Crystal Structure of Ba₂Tl₂O₅ Ba₂Tl₂O₅ was prepared and investigated by X-ray single crystal methods (space group D? Pcmn, a = 6.264, b = 17.258, c = 6.05 Å) Ba₂Tl₂O₅ is isotypic with Ca₂Fe₂O₅.     

Geordnete Oktaederbesetzung in Ba6La2Al1,5Fe2,5O15

Ordered Occupation of Octahedra in Ba₆La₂Al_1,5Fe_2,5O₁₅ Ba₆La₂Al_1.5Fe_2.5O₁₅ was prepared and investigated by X-ray single crystal technique. It crystallizes in the space group C – P6₃mc; a = 11.814, c = 7.1003 Å; Z = 2. The M³⁺O₆ octahedra are occupied exclusively by Fe³⁺ ions, the M³⁺O₄ tetrahedra in contrast are statistically filled by Fe³⁺ and Al³⁺ ions. Ba₆La₂Al_1.5Fe_2.5O₁₅ is a partially ordered mixed crystal of the pure iron and aluminium compounds.     

Über hexagonale Perowskite mit Kationenfehlstellen. III Strukturbestimmungen an Verbindungen vom Typ Ba2B □2/3 ReVIIO6

On Hexagonal Perovskites with Cationic Vacancies. III. Structure Determination on Compounds of Type Ba₂B □_2/3 Re^VIIO₆ Compounds of Type Ba₂B □_2/3 Re^VIIO₆ with B^III = rare earth, Y. Sc, In belong to the group of hexagonal perovskite stacking polytypes. For B^III = Gd, Y structure determinations with powder data have been performed. The refined R′ factors are 9.11% for Ba₂Gd1/3□_2/3ReO₆ and 12.07% for Ba₂Y1/3□_2/3ReO₆. The structure represents a rhombohedral 12 L type (space group R3 m) with the sequence hhcchhcchhcc. The lattice contains groups of three octahedra connected by common faces which are linked together by a single octahedron via common vertices. In the block of three face-sharing octahedra the central octahedral lattice site is vacant and the two outer positions are occupied by the rhenium atoms. According to this distribution direct contact of occupied face-sharing octahedra is absent.     

Über geordnete Perowskite mit Kationenfehlstellen. X. Verbindungen vom Typ ABB□1/4MVIO6 ≙ ABIIB□MO24 mit AII,BII = Ba,Sr, Ca und MVI = U,W

On Ordered Perovskites with Cationic Vacancies. X. Compounds of Type A B B □_1/4M^VIO₆ ? A B^IIB □M O₂₄ with A^II, B^II = Ba, Sr, Ca and M^VI = U, W Perovskites of type Ba₈B^IIB₂^III□UO₂₄ show polymorphic phase transformations of order disorder type. An 1:1 ordered orthorhombic HT form is transformed into a higher ordered LT modification with a fourfold cell content (four formula units Ba₈B^IIB□U₄O₂₄), compared to cubic 1:1 ordered perovskites A₂BMO₆. In the series Ba₈BaB□W₄O₂₄ and Sr₈SrB□W₄O₂₄ different ordering phenomena are observed. In comparison with 1:1 ordered cubic perovskites A₂BMO₆, the cell contains eight formula units AB^IIB□W₄O₂₄. The higher ordered cells with U^VI and W^VI are face centered, which has its origin in an ordering of cationic vacancies.     

Mononuclear Thiolatecobalt Carbonyls

A Partial Statistically Incorporation of Ca²⁺ into the Ba₆Nd₂Al₄O₁₅-Type: Ba₅CaLa₂Fe₄O₁₅ Using high temperature reactions we succeeded in incorporating Ca²⁺ into the Ba₆Nd₂Al₄O₁₅ type. Single crystal X-ray methods reveal a partly ordered alkaline earth distribution. Ba²⁺ and Ca²⁺ occupy face connected MO₆-octahedra as well as a further point position together with La³⁺ ions (space group C−P6₃mc; a = 11.770; c = 7.039 Å; Z = 2).     

Über hexagonale Perowskite mit Kationenfehlstellen. XV Ba9Nb6W□2O27 - die erste Perowskit-Stapelvariante vom rhomboedrischen 27 L-Typ

On Hexagonal Perovskites with Cationic Vacancies. XV. Ba₉Nb₆W□₂O₂₇ – the First Perovskite Stacking Polytype of Rhombohedral 27 L-Type The perovskite stacking polytype Ba₉NbW^VI□₂O₂₇(white) is the first representative of a rhombohedral 27 L-type. The lattice parameters (trigonal setting) are: a = 5.79₃ Å; c = 63.4₁ Å; Z = 3 (?_exp = 6.4₆ g/cm³; ?_calc = 6.51₂ g/cm³). The corresponding Ta^V -compound is isotypic; it tends to develop stacking faults.