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708 Zeitschrift für Kristallographie 212, 708-711 © by R. Oldenbourg Verlag, München 1997 Transmission electron microscopy evidence of a new tetragonal tungsten bronze superstructure F. Krumeich* ETH Hönggerberg, Laboratory of Solid State Physics, CH-8093 Zürich, Switzerland Received November 26, 1996; accepted in final form April 12, 1997 Abstract. Electron diffraction patterns of M56(0, F)i56 (M = Mg, Nb, W) (along [001]) exhibit eight additional spots arranged on an octagon around every reflection of the tetragonal tungsten bronze-type (TTB) substructure. Four

phases, 2.9 ≤ O/ΣM < 3.0) [ 3 ] or in two perpendicular planes forming block structures in the Nb-rich area (2.5 ≤ O/ΣM < 2.67) [ 4 ], [ 5 ]. The structures in the intermediate range are related to the tetragonal tungsten bronzes (TTB) in which four five-membered rings of corner-sharing octahedra are arranged around a central square. Some of the pentagonal tunnels are filled by metal-oxygen strings with the metals in a pentagonal bipyramid MO 7 . The array formed by the bipyramid with the adjoining five octahedra is designated a pentagonal column (PC) [ 6 ]. In Nb 8 W

1 Introduction Monophosphate tungsten bronzes (MPTBs) form a family of compounds with general composition (WO 3 ) 2 m (PO 2 ) 4 (0 ≤ m ≤ 12) [ 1 , 2 ]). Their crystal structures are built from slabs of WO 3 with ReO 3 -type structure which are separated by phosphate groups, as it is emphasized by the general formula. The alternative formulations WOPO 4 (W 4 O 4 (PO 4 ) 4 , m = 2) and W 8 O 16 (PO 4 ) 4 ( m = 4) put special emphasis on the distinction between oxygen from phosphate groups and oxide ions. In some structures the WO 3 slabs are separated by

Zeitschrift fur Physikalische Chemie Neue Folge, Bd. 157, S. 477-481 (1988) © by R. Oldenbourg Verlag, Munchen 1988 - 0044-3336/88 $3.00 + 0.00 Coulomb Gap in Sodium Tungsten Bronzes *'** Judy R. Franz Department of Physics, Indiana University, Bloomington, Indiana 47401 John H. Davies LASSP, Clark Hall, Cornell University, Ithaca, NY 14853 Recent photoemission experiments on sodium tungsten bronzes, Na Ta W, 0„, have revealed a depletion of the density of states near x y 1-y 3 the chemical potential in insulating samples. We propose that this depletion is a

Notizen 87 T h e rm io n ic E le c tro n E m ission o f T u n g s te n B ronzes. K 0 30W O 3 an d R b 0 30W O 3 F. Zocchi Istituto di Metodologie Avanzate Inorganiche, Consiglio Nazionale delle Ricerche, C.P. 10, 00016 Monterotondo Scalo, Roma, Italy Z. Naturforsch. 44a, 87-88 (1989); received November 2, 1988 The work functions and thermionic constants of the hex­ agonal tungsten bronzes K0 30WO3 ( — 1.76 eV, A = 3 A/ cm2 K2) and Rb0 30WO3 (<p = 1.88 eV, A = 10 A/cm2 K2) are determined and compared with those of the corresponding alkaline metals

Synthesis, X-ray crystal structure and dielectric measurements of a tetragonal tungsten bronze: Pb0.75K1.80Li1.70Nb5O15 M. ElaatmaniI, A. ZegzoutiI, F. Capitelli*, II, A. G. G. MoliterniII, A. MiglioriIII and G. CalestaniIV I Université Cadi Ayyad, Laboratoire de Chimie du Solide Minéral, Faculté des Sciences Semlalia, Marrakech, Maroc II CNR-IC (Institute of Crystallography), c/o Dipartimento Geomineralogico, Via Orabona, 4, I-70125 Bari, Italy III CNR-LAMEL, Via P. Gobetti n.101, I-40129 Bologna, Italy IV Università di Parma, Dipartimento di Chimica

Notizen 213 NOTIZEN Fluoride und Oxidfluoride mit hexagonaler W olframbronze-S truktur Fluorides and Oxyfluorides with H exagonal Tungsten Bronze Structure D. B a b e l Fachbereich Chemie der Universität Marburg F. B i n d e r und G. P a u s e w a n g Laboratorium für Anorganische und Analytische Chemie der Universität, Tübingen (Z. Naturforsch. 28b, 213-215 [1973]; eingegangen am 27. November 1972) Fluorides, oxyfluorides, tungsten bronze structure In Fortführung unserer Untersuchungen über Struk­ tur und Magnetismus ternärer und quaternärer Fluo­ ride 2

, Perkin-Elmer 225) von v3 , v4 , v5 (H3SiBr) und v6 bei ± 0 , 2 c m - 1 ; alle anderen Werte sind auf + 1 c m - 1 zuverlässig. Wir danken Herrn Professor Dr. H. CORDES, Braunschweig, für die Erlaubnis zur Benutzung des Cary 81, Herrn Prof. Dr. F. R. KESSLER, Braunschweig, für die Erlaubnis zu Messun- gen am PE 225, der Deutschen Forschungsgemeinschaft für die Bereitstellung der Geräte und die finanzielle Unter- stützung. Zur Struktur der Wasserstoffanaloga der Wolframbronzen Concerning the Structure of Hydrogen Analogues of Tungsten Bronzes E I N H A R D S C

Ζ. Kristallogr. NCS 216 (2001) 37-38 S© by Oldenbourg Wissenschaftsverlag, München 37 Crystal structure of rubidium niobium tungsten bronzes, RbxNb^Wi-̂ Oa (at ~ 0 . 3 ; y = 0 . 1 3 , 0 . 1 9 ) Th. M. G e s i n g * C . H. Rüscher1 and A. Hussain" 1 Universität Hannover. Institut für Mineralogie. Weifengarten I, D-30167 Hannover. Germany " University of Dhaka. Department of Chemistry. Dhaka-1000. Bangladesh Received August 24. 2000, CSD-No. 409524 and CSD-No. 409525 Discussion The crystal structures of hexagonal tungsten bronze type (HTB) can be

Ζ. Kristallogr. NCS 215 (2000) 319-320 © by Oldenbourg Wissenschaftsverlag, München 319 Crystal structure of potassium niobate, K6Nbio.8o03o, a partially filled tetragonal tungsten bronze-type structure P. Becker and P. Held* Universität zu Köln, Institut für Kristallographie, Zülpicher Str. 49b, D-50674 Köln, Germany Received December 2, 1999, CSD-No. 409464 Abstract K6Nbi0.80O30, te t ragonal , P4/mbm (No . 127), a = 12 .537(2) Ä, c = 3.9730(1) Ä, V= 624.5 Ä3, Z = 1, Rst(F) = 0.037, wRrerfF2) = 0.119, Τ =293 Κ. Source of material The title compound