Ein neues metastabiles Zinkoxovanadat: Zn4V2O9

For the first time Zn₄V₂O₉ was prepared and investigated by single crystal X-ray methods. The metastable compound exists between a CO₂-Laser generated flux and the solid ZnO/V₂O₅ material. The quenched light brown crystals show a monoclinic symmetry (space group C ₂ ² —P2₁,a=10.488 (5),b=8.198 (6),c=9.682 (5) Å; =118.66 (4)°;Z=4]. Zn₄V₂O₉ has a characteristic Zn/O-framework with incorporated V⁵⁺ in tetrahedral coordination. The relationship to Zn₄Ta₂O₉ and the calculation of the madelung part of lattice energy (MAPLE) in respect to the metastable character are discussed.

     

Zur Kenntnis von Zn4Ta2O9

About the New Compound Zn₄Ta₂O₉ The hitherto unknown compound Zn₄Ta₂O₉was prepared by high temperature reaction (CO₂-LASER technique). The X-ray investigation of single crystal shows monoclinic symmetry (space group C? C2/c) with a = 15.002(6), b = 8.954(1), c = 10.345(4)Å and β = 93.64(3)°. Zn₄Ta₂O₉ consists of a Zn/O-network with incorporated one-dimensional TaO₆-chains. The edge connected TaO₆-octahedrals are occupied by Ta⁵⁺ and 0.5 Zn²⁺ respectively. The crystal chemistry of this compound in respect to other Zn-oxotantalates are discussed.     

Experimente zur Mischkristallbildung zwischen Zinktantalaten und -antimonaten: ZnTa2−xSbxO6 und Zn4Ta2−xSbxO9

Experiments about the Mixed Crystal Formation between Zincoxotantalates and -antimonates: ZnTa_2?xSb_xO₆ and Zn₄Ta_2?xSb_xO₉ In the area of substituted oxotantalates of zinc two new phases of the composition A: ZnTa_1·8Sb_0·2O₆ and B: Zn₄Ta_1·2Sb_0·8O₉ were prepared and investigated by X-ray single crystal technique. A crystallizes with tetragonal symmetry (space group D–P4₂/mnm, a = 4.7314; c = 9.2160 Å; Z = 2). B is monoclinic (space group C–C2/c; a = 15.103; b = 8.839; c = 10.378 Å; β = 93.81°; Z = 8). A crystallizes with trirutile structure, although there is a small replacement of Ta⁵⁺ by Sb⁵⁺. B maintains the Zn₄Ta₂O₉ structure. One of the point positions of the M⁵⁺ ions is occupied statistically by Ta⁵⁺/Sb⁵⁺ and Zn²⁺. B is a metastable compound.     

Ein Beitrag zur Kristallchemie der Kobaltoxoniobate: CoNb2O6 mit Rutilstruktur

CoNb₂O₆ can be prepared by reaction of stoichiometric amounts of CoO (thermical decomposition of cobaltoxalate) and Nb₂O₅ in argon-atmosphere up to 1,400 °C. The isolated red-brown single crystals have tetragonal symmetry (a=472.6;c=305.4 pm; space group P4₂/mnm-D _4h ¹⁴ ). Electron probe micro-analysis of the single crystals verifies the composition Co_0.33Nb_0.67O₂. Co²⁺ and Nb⁵⁺ occupy statistically the metal positions of the rutil-type structure. The differences between Co_0.5Nb_0.5O₂ (CoNbO₄AlNbO₄-type) and Co_0.38Nb_0.67O₂ (CoNb₂O₆) are discussed.

     

Zur Kristallstruktur von α-TlSmW2O8

Single crystals of -TlSm(WO₄)₂ were examined by X-ray diffractometer technique (space group C _2h ⁶ -C2/c;a=10.770,b=10.597,c=7.597 Å, =130.09°,Z=4). The coordination of W⁶⁺, Sm³⁺ and Tl⁺ are discribed and discussed.-TlSm(WO₄)₂ is isotypic to -KY(WO₄)₂.

     

Crystal structures and dielectric properties of ordered double perovskites containing Mg and Ta

The ordered double perovskites ALaMgTaO₆ (A=Ba, Sr, Ca) and La₂Mg(Mg_1/3Ta_2/3)O₆ have been prepared and characterized. Synchrotron X-ray powder diffraction analyses show that all four compounds exhibit a rock-salt type ordering of the B-site cations (Mg²⁺/Ta⁵⁺) and a random distribution of A-site cations (A²⁺/La³⁺). The space group symmetries are determined to be for BaLaMgTaO₆, and P2₁/n for SrLaMgTaO₆, CaLaMgTaO₆, and La₂Mg(Mg_1/3Ta_2/3)O₆. Diffuse-reflectance spectroscopy shows these ordered perovskites have optical band gaps in the range of 4.6−4.8 eV. These values are roughly 1 eV wider than the ternary perovskite oxides of Ta⁵⁺ such as KTaO₃, due to narrowing of the conduction bandwidth which results from Mg²⁺/Ta⁵⁺ ordering. These compounds are insulators with dielectric permittivities of κ=18-23, dielectric losses of tan δ=0.004-0.007, and small temperature coefficients of capacitance <100 ppm/K over the temperature range 20-150 °C. BaLaMgTaO₆ is of particular interest because it possesses a near-zero temperature dependence of capacitance.     

Über ein neues Oxoiridat(IV): Ba7Ir6O19

Summary The so far unknown compound Ba₇Ir₆O₁₉ was prepared by long time solid state reactions using a flux of BaCl₂. X-ray single crystal work lead to the space group C _2h ³ —C2/m;a=14.913;b=5.778;c=10.979 Å; =99.58°;Z=2. It crystallizes with a new structure type characterized by three face-shared octahedra. The Ir₃O₁₂-groups build up a threedimensional network with an incorporated Ba/O-frame.

     

Präparation und röntgenographische Untersuchung eines neuen Kupfer-Oxoaluminats: Cu2Al4O7

Solid state reaction of CuO and Al₂O₃ with a flux of PbO about 930°C and reaction time of 8d gives the new compound Cu₂Al₄O₇. The red single crystals were examined by energydispersive microanalysis and X-ray diffraction methods. Cu₂Al₄O₇ has cubic symmetry, space group ,a=908.0 pm. The typical coordination of Cu⁺ (CN=6 and CN=12) and the interstitial arrangement of the AlO₄-tetrahedra are discussed with respect to related compounds.

     

Crystal structure of Li2Cu3(SeO3)2(SeO4)2

Summary Single crystal X-ray data of the hydrothermally grown new phase Li₂Cu₃(SeO₃)₂(SeO₄)₂ were measured with a four-circle diffractometer up to sin /=0.81 Å^–1 [I2/a,Z=4,V=1175.5 ų,a=16.293(6),b=5.007(2),c=14.448(6) Å, = 94.21(1)°]. The structure was determined by direct and Fourier methods and refined toR=0.034,R _w =0.027 for 2 086 independent reflections.Cu(1)^[4+1]O₅ forms a tetragonal pyramid, Cu(2)^{[4 + 2]}O₆ is a strongly elongated octahedron. The Li atom is surrounded by four O atoms forming a distorted tetrahedron. Se(IV)O₃ and Se(VI)O₄ groups are in accordance to literature, mean Se-O bond lengths are 1.714 and 1.644 Å.

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Die Kristallstruktur von Li₂Cu₃(SeO₃)₂(SeO₄)₂

Zusammenfassung Einkristall-Röntgendaten der hydrothermal gezüchteten neuen Phase Li₂Cu₃(SeO₃)₂(SeO₄)₂ wurden mit einem Vierkreisdiffraktometer im Bereich bis zu sin /=0.81 Å^–1 gemessen [I2/a,Z=4,V=1175.5 ų,a=16.293(6),b=5.007(2),c=14.448(6) Å, =94.21(1)°]. Die Kristallstruktur wurde mittels direkter und Fourier-Methoden bestimmt und für 2 086 unabhängige Reflexe zuR=0.034,R _w =0.027 verfeinert.Cu(1)^[4+1]O₅ bildet eine tetragonale Pyramide, Cu(2)^[4+2]O₆ ist ein stark verlängertes Oktaeder. Das Li-Atom ist von vier O-Atomen in Gestalt eines verzerrten Tetraeders umgeben. Die Se(IV)O₃-und Se(VI)O₄-Gruppen entsprechen der Literatur, die mittleren Se-O-Abstände betragen 1.714 und 1.644 Å.

     

Kinetik der Entladung von Zn2+ und Ni2+ an der Quecksilbertropfelektrode in einem Thiomalatmedium

Zusammenfassung Wir untersuchten auf polarographischem Wege die Kinetik der Entladung von Zn²⁺ und Ni²⁺ an der Quecksilbertropfelektrode in einem Thiomalatmedium konstanter Ionenstärke (=0,5). Wir stellten fest, daß die Reduktion von Zn²⁺ und Ni²⁺ irreversibel verläuft und berechneten daher die kinetischen Parameter (Übertragungskoeffizient , Geschwindigkeitskonstante der HinreaktionK _f,h ^o ) nach dem theoretischen Verfahren vonKoutecky in der vonMeites undIsrael erweiterten Form.

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Kinetics of discharge of Zn²⁺ and Ni²⁺ at the D.M.E. in thiomalate media

Kinetics of discharge of Zn²⁺ and Ni²⁺ have been studied polarographically in thiomalate media of constant ionic strength (=0.5) at the dropping mercury electrode. The reduction of both Zn²⁺ and Ni²⁺ was found to be irreversible. Hence, the kinetic parameters (transfer coefficient , and forward rate constantK _j,h ^o ) have been calculated byKoutecky's theoretical treatment as extended byMeites andIsrael.

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Die Kristallstruktur von Pb3GeAl10O20 (Pb3SiAl10O20)

Zusammenfassung Die Kristallstruktur von Pb₃GeAl₁₀O₂₀ und der dazu isotypen Verbindung Pb₃SiAl₁₀O₂₀ wird bestimmt (R=0,16). Die Gitterparameter der monoklinen, pseudorhombischen Zelle (Raumgruppe I2/m–C _2h ³ ;Z=2) sind:a=14,39;b=11,44;c=5,004 Å und =90,0 für Pb₃GeAl₁₀O₂₀ und:a=14,34;b=11,39;c=4,96 und =90,0 für Pb₃SiAl₁₀O₂₀. Das Gerüst besteht aus AlO₄-Tetraedern und AlO₆-Oktaedern, wobei Germanium und Aluminium statistisch über die Plätze 2b, 4h, 8j und 8j verteilt sind. Die Bleiatome sitzen in Kanälen parallel zu [001] in 2a und 4i. Die verschiedene Umgebung der Pb-Atome auf den beiden Plätzen wird diskutiert.

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The crystal structure of Pb₃GeAl₁₀O₂₀ (Pb₃SiAl₁₀O₂₀)

The crystal structure of Pb₃GeAl₁₀O₂₀ and Pb₃SiAl₁₀O₂₀, an isotypic compound, has been determined (R=0.16). The lattice parameters were found to be:a=14.39 Å;b=11.44 Å;c=5.004 Å, and =90.0 for Pb₃GeAl₁₀O₂₀ and:a=14.34 Å;b=11.39 Å;c=4.96 Å and =90.0 for Pb₃SiAl₁₀O₂₀;Z=2, space group I2/m–C³ _2h. The network consists of AlO₄ tetrahedra and AlO₆ octahedra; germanium atoms are randomly distributed at the positions of the Al-atoms 2b, 4h, 8j, and 8j. The lead atoms occupy the positions 2a and 4i within channels in the network parallel to [001]. The different environment of the two kinds of lead atoms will be discussed.

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Zur Kristallchemie von Ba3In2Zn5O11. Ein tOxoindat/zinkatsol;zinkat mit Zn10O20- und In4O16-Makropolyedern und erstmals O2− in tetraedrischer Koordination durch Zn2+

On the Crystal Structure of Ba₃In₂Zn₅O₁₁. An Oxoindate/zincatesol;zincate with Zn₁₀O₂₀ and In₄O₁₆ Macropolyhedra with Zn²⁺ in Tetrahedral Coordination by O^2? Ba₃In₂Zn₅O₁₁ was prepared for the first time by a flux technique and investigated by single crystal X-ray work. It crystallizes with cubic symmetry, space group T-F4 3m, a = 13.3588 Å, Z = 8. Zn²⁺ show tetrahedral coordination by O^2?, forming Zn₁₀O₂₀ macropolyhedra. In addition the nZn/Osol;O part of the crystal structure is made up of Zn₁₀O₂₀ parts. Edge connection of four InO₆ octahedra results in In₄O₁₆ groups. The crystal structure will be shown and discussed.     

Zur Kristallchemie der tetragonalen Wolframbronze: Ba6FeNb9O30

Solid state reaction of BaCO₃, FeC₂O₄·2H₂O and Nb₂O₅ gave single crystals of Ba₆FeNb₉O₃₀. The crystal structure was solved by X-ray investigations (a=12.597,c=3.990Å, space group P 4 bm-C _4v ² ,Z=1). Ba₆FeNb₉O₃₀ crystallyzes in the tetragonal bronze type with a statistical distribution of Fe³⁺ and Nb⁵⁺ in the octahedral framework. The anisotropic temperature factors of barium are discussed with respect to the oxygen coordination.

     

Natural product chemistry,part 100: The structure of carissone,C15H24O2

Summary C₁₅H₂₄O₂,M=236.2, monoclinic, P 2₁,a=7.229(7),b=14.925 (9),c=6.235 (9) Å, =92.40 (9)°,V=672.1 ų,T=–133 °C,Z=2,D _x=1.17 g cm^–3. The X-ray diffraction analysis of this sesquiterpenoid fromCarissa opaca confirmed the previously proposed constitution of the isolate and, furthermore, allowed precise NMR assignment.

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Naturstoffchemie, 100. Mitt.: Die Struktur des Carissons, C₁₅H₂₄O₂

Zusammenfassung C₁₅H₂₄O₂,M=236.2, monoklin, P 2₁,a=7.229 (7),b=14.925 (9),c=6.235 (9) Å, =92.40 (9)°,V=672.1 ų,T=–133 °C,Z=2,D _x=1.17 g cm^–3. Die Röntgenstrukturanalyse dieses Sesquiterpenoids ausCarissa opaca bestätigte die bereits vorgeschlagene Struktur und erlaubte ferner eine genaue NMR-Zuordnung.

     

Über den Einbau von Fremdionen in γ-Al2O3, 5. Mitt.: Spektroskopische Untersuchungen

Zusammenfassung Der Einbau von Fremdionen in -Al₂O₃ wurde mittels Reflexionsspektroskopie untersucht. Als Kristallfeldindikator wurde Cr³⁺ verwendet. Um den Einfluß tetraedrisch koordinierter Kationen auf das Chromspektrum zu untersuchen, wurde Zn²⁺, Cd²⁺, Ga³⁺ und Ge⁴⁺ zusätzlich eingebaut. Der Einfluß oktaedrisch koordinierter Kationen wurde an Cr³⁺ und Sn⁴⁺ untersucht. Aus der Verschiebung des Chromspektrums durch den Einbau von Ca²⁺, Sr²⁺ und Ba²⁺ in -Al₂O₃ wurde die Art des Einbaues dieser Kationen bestimmt und der Mechanismus einer Stabilisierung von -Al₂O₃ durch Einbau von Fremdionen diskutiert.

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Reflection spectroscopy has been used to investigate the incorporation of foreign ions into -Al₂O₃, Cr³⁺ serving as a crystal field indicator. Zn²⁺, Cd²⁺, Ga³⁺ and Ge⁴⁺ where built in additionally to test the influence of tetrahedrally coordinated cations. The influence of cations with octahedral coordination was investigated by means of Cr³⁺ and Sn⁴⁺. The shift in the chromium spectrum observed after the incorporation of Ca²⁺, Sr²⁺ and Ba²⁺ was used to determine the type of incorporation. A mechanism of stabilisation of -Al₂O₃ after introduction of foreign ions is discussed.

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H. Krischner, K. Torkar, R. Hoffmann undD. Donnert,4. Mitt., Mh. Chem.99, 1080 (1968).     

Die Kristallstruktur des Lithium-enneagermanats Li4[Ge9O20]

The crystal structure of lithium enneagermanate, Li₄[Ge₉O₂₀], has been determined and refined by least-squares, using three-dimensional single-crystal data. The compounds crystallizes with monoclinic symmetry (a=12.43,b=8.00,c=7.49 Å, =91.0^o; C2–C₂ ³) building up a framework structure which exhibits some similarity with the structures of Li₂[Ge₄O₉] and Li₂[Ge₇O₁₅]. Out of the 18 Ge-atoms in the unit cell 14 are surrounded tetrahedrally by oxygen showing an average distance of 1.757 Å; the remaining 4 Ge-atoms are octahedrally coordinated with an average distance of 1.886 Å.

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Die Kristallstruktur des Lithium-enneagermanats Li₄[Ge₉O₂₀]

Zusammenfassung Die Kristallstruktur von Lithium-enneagermanat Li₄[Ge₉O₂₀] wird an Hand dreidimensionaler Einkristalldaten ermittelt und nach der Methode der kleinsten Quadrate verfeinert (R=0,083). Die monoklin kristallisierende Verbindung (a=12,43;b=8,00;c=7,49 Å; =91,0^o; C2–C₂ ³) besitzt eine Gerüstruktur, die einen ähnlichen Aufbau wie Li₂[Ge₄O₉] und Li₂[Ge₇O₁₅] zeigt. Von den 18 Ge-Atomen in der Elementarzelle liegen 14 in tetraedrischer Koordination mit einem mittleren Ge–O-Abstand von 1,757 Å vor; 4 Ge-Atome sind oktaedrisch umgeben, mit einem mittleren Ge–O-Abstand von 1, 1886 Å.

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Herrn Professor Dr.O. Hromatka zum 65. Geburtstag gewidmet.     

Phase equilibria in the system La2O3-Na2O-P2O5

In the ternary system La₂O₃-P₂O₅-Na₂O the partial system La₂O₃-Na₄La₂P₄O₁₅-LaPO₄ has been examined by the thermal, dilatometric X-ray and microscopic analyses and its phase diagram provided. The lanthanum oxyphosphate La₃PO₇ melts incongruently at the 1590°C temperature and crystallizes in a monoclinic systema=11.20 Å,b=11.94 Å,c=7.01 Å,=93.79 andV=936.97 ų.

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Zusammenfassung Mittels Thermo- und dilatometrischer Analyse, Röntgendiffraktionsuntersuchungen und Mikroskopie wurde das Teilsystem La₂O₃ - Na₄La₂P₄O₁₅ - LaPO₄ des ternären Systemes La₂O₃ - P₂O₅ - Na₂O untersucht und ein Phasendiagramm entwickelt. Lanthanoxyphosphat La₃O₇ schmilzt inkongruent bei 1590°C und kristalliert in einem monoklinen System mita=11.20 Ä,b=11.94 Ä,c=7.01 Å,=93.79 undV=936.97 ų.

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The author thanks Mrs. B. Lagódka for the technical assistance (thermogravimetric analyses). The thermal study was supported by grant CPBP.     

Neue Phasen in den Systemen Nb2O5-WO3 und Ta2O5-WO3

Zusammenfassung Bei Untersuchungen im WO₃-ärmeren Bereich der Systeme Nb₂O₅-WO₃ und Ta₂O₅-WO₃ bis zum Molverhältnis Me₂O₅:WO₃=1:2 wurden folgende Phasen neu gefunden: 40 Nb₂O₅·WO₃–20 Nb₂O₅·WO₃ (Phasenbreite), 13 Nb₂O₅· ·4 WO₃, 9 Nb₂O₅·8 WO₃ (Tieftemperaturphase), 9 Ta₂O₅· ·8 WO₃; ferner eine Mischphase des T-Ta₂O₅, die bis zur Zusammensetzung 13 Ta₂O₅·4 WO₃ (bei 1300° C) reicht. Weitere Phasen wurden im System Nb₂O₅-WO₃ bei den Molverhältnissen 8:1–6: 1, 7:3, 8:5 und 9:8 (Hochtemperaturphase) beobachtet.49. Mitt.:H. Schäfer, R. Gruehn undF. Schulte, Angew. Chemie, im Druck.     

Die Kristallstruktur von Rb6Si10O23

Zusammenfassung Die Kristallstruktur der Verbindung Rb₆Si₁₀O₂₃ (bisher als Rb₂Si₄O₉ beschrieben) wurde mit Hilfe dreidimensionaler Röntgendaten bestimmt und bis zu einemR-Wert von 0,078 verfeinert. Die Gitterparameter der rhombischen Elementarzelle (C2mm-C _2v ¹⁴ ) betragen:a=9,348,b=16,290 undc=8,055 Å. Die Struktur besitzt ein dreidimensionales Gerüst aus [SiO₄]-Tetraedern, die sowohl über 4 als auch über 3 Ecken vernetzt vorliegen. Die Anordnung der Tetraeder kann aus der Tridymitstruktur abgeleitet werden und zeigt noch deutlich pseudohexagonale Symmetrie. Bei 500 °C geht die Verbindung in eine Hochtemperaturform mit hexagonaler Symmetrie über (a=9,48 undc=8,16 Å bei 500 °C).

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The crystal structure of Rb₆Si₁₀O₂₃

The crystal structure of the compound Rb₆Si₁₀O₂₃ (identical with Rb₂Si₄O₉) has been determined by means of three-dimensional X-ray data resulting anR-value of 0.078. The lattice parameters of the orthorhombic unit cell (C2mm-C _2v ¹⁴ ) are:a=9.348,b=16.290 andc=8.055 Å. The structure consists of a three-dimensional framework built up by [SiO₄] tetrahedra sharing 4 as well as 3 corners. The arrangement of tetrahedra can be derived from tridymite structure and exhibits pseudohexagonal symmetry. The compound transforms to a high-temperature modification with hexagonal symmetry at 500 °C (a=9.48 andc=8.16 Å).

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Composition-induced phase transition in Ca14Zn6−xGa10+xO35+x/2 (x=0.0 and 0.5)

Novel complex oxides Ca₁₄Zn₆Ga₁₀O₃₅ and Ca₁₄Zn_5.5Ga_10.5O_35.25 were prepared in air at 1200 °C, 72 h. Refinements of their crystal structures using X-ray powder diffraction data showed that Ca₁₄Zn₆Ga₁₀O₃₅ is ordered (S.G. F23, =0.0458, R_p=0.0485, R_wp=0.0659, χ²=1.88) and Ca₁₄Zn_5.5Ga_10.5O_35.25 disordered (S.G. F432, =0.0346, R_p=0.0601, R_wp=0.0794, χ²=2.82) variants of the crystal structure of Ca₁₄Zn₆Al₁₀O₃₅. In the crystal structure of Ca₁₄Zn₆Ga₁₀O₃₅, there are large empty voids, which could be partially occupied by additional oxygen atoms upon substitution of Zn²⁺ by Ga³⁺ as in Ca₁₄Zn_5.5Ga_10.5O_35.25. These oxygen atoms are introduced into the crystal structure of Ca₁₄Zn_5.5Ga_10.5O_35.25 only as a part of four tetrahedra (Zn, Ga)O₄ groups sharing common vertex. This creates a situation where even a minor change in the chemical composition leads to considerable anion and cation disordering resulting in a change of space group from F23 (no. 196) to F432 (no. 209).