A new triple molybdate, Rb2Ag1+3x In1–x (MoO4)3 (0 ≤ x ≤ 0.02), was found in the course of a study of the system Rb2MoO4–Ag2MoO4–In2(MoO4)3 and was synthesized as both powders and single crystals by solid-state reactions and spontaneous crystallization from melts. The structure of Rb2Ag1+3x In1–x (MoO4)3 (x ≈ 0.004) is of a new type crystallizing in the centrosymmetric space group R\overline{3}c [a = 10.3982 (9), c = 38.858 (4) Å, Z = 12 and R = 0.0225] and contains (In,Ag)O6 octahedra and distorted Ag1O6 trigonal prisms linked by common faces to form [Ag(In,Ag)O9] dimers connected to each other via MoO4 tetrahedra into an open three-dimensional (3D) framework. Between two adjacent [Ag(In,Ag)O9] dimers along the c axis, an extra Ag2O6 trigonal prism with about 1% occupancy was found. The Ag1O6 and Ag2O6 prisms are located at levels of z ≈ 1/12, 1/4, 5/12, 7/12, 3/4 and 11/12, and can facilitate two-dimensional ionic conductivity. The 12-coordinate Rb atoms are in the framework cavities. The structure of Rb2AgIn(MoO4)3 is a member of the series of rhombohedral 3D framework molybdate structure types with a ≈ 9–10 Å and long c axes, which contain rods of face-shared filled and empty coordination polyhedra around threefold axes. Electrical conductivity of ceramics is measured by impedance spectroscopy. Rb2AgIn(MoO4)3 undergoes a `blurred' first-order phase transition at 535 K with increasing electrical conductivity up to 1.1 × 10−2 S cm−1 at 720 K. Thus, the compound may be of interest for developing new materials with high ionic conductivity at elevated temperatures.
New compounds of the composition Na5Rb7Sc2(XO4)9 (X = Mo, W) were obtained via the ceramic technology. The sequences of chemical transformations occurring during the formation of these compounds were established, and their primary characterization was performed. Both Na5Rb7Sc2(XO4)9 (X = Mo, W) were found to melt incongruently at 857 K (X = Mo) and 889 K (X = W). They are isostructural to Ag5Rb7Sc2(XO4)9 (X = Mo, W), Na5Cs7Ln2(MoO4)9 (Ln = Tm, Yb, Lu) and crystallize in the trigonal crystal system (sp. gr. R32). The crystal structures were refined with the Rietveld method using the powder X-ray diffraction data. The thermal expansion of Na5Rb7Sc2(WO4)9 was studied by high-temperature powder X-ray diffraction; it was shown that this triple tungstate belongs to high thermal expansion materials.
Triple molybdates one-, one -and three(two)valence metalsthe review summarizes experimental data on the phase formation, structure and properties of new complex oxide compounds group -triple molybdates containing tetrahedral molybdate ion, two different singly charged cation, together with tri-or divalent cation. The several structural families of these compounds were distinguished and it shown that many of them are of interest as luminescent, laser, ion-conducting or nonlinear optical materials.Keywords: triple molybdates, one-, two -and trivalent metals, phase formation, structure, functional properties. The work is executed at partial support of the Russian Foundation for basic research (projects No. 08-03-00384, 13-03-01020 and 14-03-00298).© Khaikina G. E., Solodovnikov S. F., Basovich O. M., Solodovnikova Z. A., Kadyrova Y. M., Savina A. A., Zolotova E. S., Yudin V. N., Spiridonova T. S., 2015The molybdates and tungstates are among the most popular objects of inorganic chemistry, crystal chemistry and solid state chemistry, as well as a base for developing of functional materials for various purposes, which maintains a constant interest in these compounds and explains a significant number of publications on this subject. In the last two decades there has been a shifting of the centre gravity of studies from double molybdates and tungstates on triple molybdates. To date, this group of compounds has more than 550 individuals and is the fastest growing of complex oxide phases containing tetrahedral anion and cation. The large part of triple molybdates is prepared and is characterized by the employees of the Baikal Institute of nature management SB RAS (Ulan-Ude) and the Institute of inorganic chemistry named A. V. Nikolaev SB RAS (Novosibirsk). A brief overview of the different types of triple molybdates, different combinations of the charges of their constituent cations is earlier presented in [6]. The aim of this work is a detailed consideration of the phase formation, structure and properties of triple molybdates, containing two different singly mono-charged cation along with triple-charged (type 1-1-3) or doubly charged (type 1-1-2) cation. Triple molybdates of the type 1-1-3The first systematic searching researches of triple molybdates of one-, one-, and trivalent metals were conducted for lithium-containing systems Li 2 MoO 4 - phases in a series of REE vary significantly and with increasing size of singly charged cations move in the direction to the light lanthanides (Fig. 2).The analysis of experimental data allows to draw a conclusion about the decisive influence of dimensional factor on the possibility of the formation of monoclinic triple molybdates of this family: LiMLn 2 (MoO 4 ) 4 are formed, if the difference in sizes of ions of large singly charged cation and rare earth element lies in the interval. 0.48At lower values of Dr in the cut of LiLn(MoO 4 ) 2 -MLn(MoO 4 ) 2 there is the formation of solid solutions. When Dr > 0.60 Å the consider phase is either not formed or its formation is so comp...
Two new isostructural compounds, namely heptapotassium silver tetrakis(tetraoxomolybdate), KAg(MoO) (0 ≤ x ≤ 0.4), and heptapotassium silver tetrakis(tetraoxotungstate), KAg(WO) (0 ≤ x ≤ 0.4), have been synthesized and found to crystallize in the polar space group P6mc (Z = 2) with the unit-cell dimensions a = 12.4188 (2) and c = 7.4338 (2) Å for KAg(MoO) (single-crystal data), and a = 12.4912 (5) and c = 7.4526 (3) Å for KAg(WO) (Rietveld analysis data). Both structures represent a new structure type, with characteristic [K1(XO)] `pinwheels' of K1O octahedra and six XO tetrahedra (X = Mo, W) connected by common opposite faces into columns along the c axes. The octahedral columns are linked to each other through Ag1O tetrahedra along with the K2 and K3/Ag2 polyhedra, forming the polar rods (...Ag1O-X1O-empty octahedron-Ag1O...). Ag1 is located almost at the centre of the largest face of its coordination tetrahedron and seems to have some mobility. The new structure type is related to the BaNdAlO and CaBaSiO types, and to other structures of the α-KSO-glaserite family. The differential scanning calorimetry (DSC) and second harmonic generation (SHG) results show that both compounds undergo first-order phase transformations to high-temperature centrosymmetric phases.
В исследовании и получении новых фаз с ценными физико-химическими свойствами важное место отводится тройным соединениям с тетраэдрическим анионом, содержащим различные комбинации одно- и поливалентных катионов, в частности, тройным молибдатам и вольфраматам. Интерес представляют серебросодержащие тройные молибдаты AgA3R(MoO4)5, принадлежащие к структурному типу NaMg3In(MoO4)5 (триклинная сингония, пр. гр. P1, Z = 2) и обладающие достаточно высокой ионной проводимостью (10–3–10–2 См/cм). В связи с этим, целью даннойработы явилось установление возможности образования подобных соединений в молибдатных и вольфраматных системах серебра, цинка, индия и железа и выявление влияния природы тетраэдрического аниона и трехзарядных катионов на их получение и свойства.Синтез поликристаллических образцов осуществляли по керамической технологии. Методами исследования являлись дифференциально-термический и рентгенофазовый анализы.В результате выполнения работы получены новые тройные молибдаты AgZn3R(MoO4)5 (R = In, Fe), кристаллизующиеся в триклинной сингонии (пр. гр. P1, Z = 2). Определены последовательность химических превращений, протекающих при образовании этих соединений, их кристаллографические и термические характеристики. Параметры элементарной ячейки для индиевого соединения: a = 6.9920(4), b = 7.0491(4), c = 17.9196(9) Å, a = 87.692(5), b = 87.381(5),g = 79.173(5)°; для железного: a = 6.9229(3), b = 6.9828(4), c = 17.7574(8) Å, a = 87.943(4), b = 87.346(5), g = 78.882(5)°.Установлено, что серебросодержащие тройные вольфраматы цинка с индием и железом, обладающие подобной структурой, не образуются. ЛИТЕРАТУРА 1. Котова И. Ю. Фазообразование в системе сучастием молибдатов серебра, кобальта и алюми-ния. Журнал неорганической химии. 2014;59(8):1066–1070. DOI: https://doi.org/10.7868/s0044457x140801332. Kotova I. Yu., Korsun V. P. Phase in the Ag2MoO4–MgMoO4–Al2(MoO4)3. Russ. J. Inorg. Chem. 2010;55(6):955–958. DOI: https//doi.org/10.1134/S00360236100602033. Kotova I. Yu., Korsun V. P. Phase formation inthe system involving silver, magnesium, and indiummolybdates. Russ. J. Inorg. Chem. 2010;55(12): 1965–1969. DOI: https//doi.org/10.1134/S00360236101202474. Kotova I. Yu., Belov D. A., Stefanovich S. Yu.Ag1–xMg1–xR1+x(MoO4)3 Ag+-conducting NASICON-likephases, where R = Al or Sc and 0 ≤ x ≤ 0.5. Russ. J. Inorg.Chem. 2011;56(8): 1189−1 193. DOI: https//doi.org/10.1134/S00360236110801225. Bouzidi C., Frigui W., Zid M. F. Synthèseet structure cr ystalline d'un matériau noirAgMnII 3(MnIII 0.26Al0.74)(MoO4)5. Acta CrystallographicaSection E Crystallographic Communications. 2015;71(3): 299–304. DOI: https//doi.org/10.1107/S20569890150033456. Nasri R., Chérif S. F., Zid M. F. Structure cristallinede la triple molybdate Ag0.90Al1.06Co2.94(MoO4)5. ActaCrystallographica Section E Crystallographic Communications.2015; 71(4): 388−391. DOI: https//doi.org/10.1107/s20569890150052907. Kotova I. Yu., Solodovnikov S. F., SolodovnikovaZ. A., Belov D. A., Stefanovich S. Yu., Savina A. A.,Khaikina E. G. New series of triple molybdatesAgA3R(MoO4)5 (A = Mg, R = Cr, Fe; A = Mn, R = Al, Cr,Fe, Sc, In) with framework structures and mobile silverion sublattices. Journal of Solid State Chemistry.2016;238: 121–128. DOI: https//doi.org/10.1016/j.jssc.2016.03.0038. Балсанова Л.В. Синтез кристаллов серебро-содержащих оксидных фаз на основе молибдена,изучение их структуры и свойств. Вестник ВСГУТУ. 2015;5: 63−69.9. Kotova I. Yu., Savina A. A., Khaikina E. G. Crystalstructure of new triple molybdate AgMg3Ga(MoO4)5from Rietveld refinement. Powder Diffraction.2017;32(4): 255–260. DOI: https//doi.org/10.1017/S088571561700081110. Kotova I. Yu., Savina A. A., Vandysheva A. I.,Belov D. A., Stefanovich S. Yu. Synthesis, cristal struc-ture and electrophysical properties of triple molybdatescontaining silver, gallium and divalent metals.Chimica Techno Acta. 2018;5(3): 132–143. DOI: https://doi.org/10.15826/chimtech.2018.5.3.0211. Klevtsova R. F., Vasiliev A. D., KozhevnikovaN. M., Glinskaya L. A., Kruglik A. I., Kotova I. Yu.Synthesis and crystal structural study of ternary molybdateNaMg3In(MoO4)5. Journal of StructuralChemistry. 1994;34(5): 784−788. DOI: https://doi.org/10.1007/BF0075358012. Hermanowicz K., Maczka M., Wolcyrz M., TomaszewskiP. E., Paściak M., Hanuza J. Crystal structure,vibrational properties and luminescence ofNaMg3Al(MoO4)5 crystal doped with Cr3+ ions. Journalof Solid State Chemistry. 2006;179(3): 685–695. DOI:https://doi.org/10.1016/j.jssc.2005.11.03213. Rietveld H. M. A profile refinement method fornuclear and magnetic structures. Journal of AppliedCrystallography. 1969;2: 65–71. DOI: https://doi.org/10.1107/s002188986900655814. Kohlmuller R., Faurie J.-P. Etude des systemesMoO3–Ag2MoO4 et MoO3–MO (M – Cu, Zn, Cd). Bull.Soc. Chim. France. 1968;11: 4379–4382.15. Трунов В. К., Ковба Л. М. О взаимодействииIn2O3 с WO3 и MoO3. Вестник Московского универ-ситета. Химия. 1967;1: 114–115.16. Трунов В. К., Ковба Л. М. О взаимодействиитрехокисей молибдена и вольфрама с полуторны-ми окисями железа и хрома. Известия АН СССР.Неорган. Материалы. 1966;2: 151–154.17. ICDD PDF-2 Data Base, Cards ## 00-049-0337,00-035-0765, 01-073-0554, 01-083-1701, 01-074-1791.18. Smith G. S., Snyder R. L. FN: A criterion forrating powder diffraction patterns and evaluating thereliability of powder-pattern indexing. Journal ofApplied Crystallography. 1979;12(1): 60–65.DOI: https//doi.org/10.1107/S002188987901178X19. Shannon R. D. Revised effective ionic radii andsystematic studies of interatomic distances in dalidesand chalcogenides. Acta Crystallographica Section A.1976; 32(5): 751–767. DOI: https://doi.org 10.1107/S056773947600155120. Порай-Кошиц М. А., Атовмян Л. О. Кристаллохимия и стереохимия координационных соединений молибдена. М.: Наука; 1974. 230 c.
The Ag2MoO4–Cs2MoO4 system was studied by powder X-ray diffraction, the formation of a new double molybdate CsAg3(MoO4)2 was established, its single crystals were obtained, and its structure was determined. CsAg3(MoO4)2 (sp. gr. P3¯, Z = 1, a = 5.9718(5), c = 7.6451(3) Å, R = 0.0149) was found to have the structure type of Ag2BaMn(VO4)2. The structure is based on glaserite-like layers of alternating MoO4 tetrahedra and Ag1O6 octahedra linked by oxygen vertices, which are connected into a whole 3D framework by Ag2O4 tetrahedra. An unusual feature of the Ag2 atom environment is its location almost in the centre of an oxygen face of the Ag2O4 tetrahedron. Caesium atoms are in cuboctahedral coordination (CN = 12).We determined the structures of the double molybdate of rubidium and silver obtained by us previously and a crystal from the solid solution based on the hexagonal modification of Tl2MoO4, which both are isostructural to glaserite K3Na(SO4)2 (sp. gr. P3¯m1). According to X-ray structural analysis data, both crystals have nonstoichiometric compositions Rb2.81Ag1.19(MoO4)2 (a = 6.1541(2), c = 7.9267(5) Å, R = 0.0263) and Tl3.14Ag0.86(MoO4)2 (a = 6.0977(3), c = 7.8600(7) Å, R = 0.0174). In the case of the rubidium compound, the splitting of the Rb/Ag position was revealed for the first time am ong molybdates. Both structures are based on layers of alternating MoO4 tetrahedra and AgO6 or (Ag, Tl)O6 octahedra linked by oxygen vertices. The coordination numbers of rubidium and thallium are 12 and 10
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