Chapter 3 - The Oxide Chemistry of Molybdenum
About: This article is published in Studies in Inorganic Chemistry.The article was published on 1994-01-01. It has received 19 citations till now. The article focuses on the topics: Molybdenum & Oxide.
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31 Oct 1956
TL;DR: In this article, a mass spectometric analysis of the vapor in thermodynamic equilibrium with powdered molybdenum trioxide, as sampled from a Knudsen effusion cell, has shown that the vapor phase consists of Mo3O9, Mo4O12 and Mo5O15 molecules.
Abstract: Mass spectometric analysis of the vapor in thermodynamic equilibrium with powdered molybdenum trioxide, as sampled from a Knudsen effusion cell, has shown that the vapor phase consists predominantly of Mo3O9, Mo4O12 and Mo5O15 molecules. Utilizing the Clausius‐Clapeyron equation, individual heats of sublimation have been determined to be 80.5±1.5, 93.6±1.6 and 105.6±3.5 kcal/mole respectively at 850° K. The heats of formation and third law entropies have been evaluated for each of these molecules.
112 citations
TL;DR: In this article, the role of 2-aminopyridine (2ampy) in the formation of the different solids under hydrothermal conditions is discussed, and the structures of these materials were established by single-crystal and powder X-ray diffraction techniques.
Abstract: The hydrothermal reaction of an aqueous ammonium heptamolybdate solution with first-row transition metal salts in the presence of 2-aminopyridine at around 180 °C and under autogenous pressure yields several molybdates, such as the 1D chains in (C5N2H7)4Mo8O26 (1), zero-dimensional (C5N2H7)6Mo7O24·3H2O (2), and the first synthesis of Lindgrenite [Cu3Mo2O8(OH)2 (3)] The structures of these materials were established by single-crystal and powder X-ray diffraction techniques. The crystal structures of wolframite-based MnMoO4 (4) and ZnMoO4 (5) were established by powder X-ray diffraction. The role of 2-aminopyridine (2-ampy) in the formation of the different solids under hydrothermal conditions is discussed. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005)
81 citations
TL;DR: In this article, a chemical etching method has been developed for restructuring these thermally processed catalysts using a 0.1 M NaOH etchant, where the surface steps, ledges, and terraces are created.
Abstract: Crystalline catalysts of orthorhombic MoO3 have been prepared via a vapor phase deposition method, and their crystallographic structure has been affirmed by XRD and FTIR investigations. A chemical etching method has been developed for restructuring these thermally processed catalysts. Using a 0.1 M NaOH etchant, {001} and {100} plane areas of the catalysts can be significantly increased while surface steps, ledges, and terraces are created. Moreover, alternate crystal plane combinations of either {100} and {010} or the {001} and {010} are observed on crystal edges and rectangular etch pits in the basal planes {010}. Both materials chemistry of MoO3 and etching mechanisms have been studied on the basis of the surface morphological evolution of etching patterns of the catalysts. Technological merits and the processing parameters of this new method have also been identified. Following the findings of the current work, it is believed that the chemically carved surface structures may be crucial for certain MoO...
72 citations
TL;DR: In this article, a review of the benefits and methods for interlayer modification of layered transition metal oxides, which include the presence of structural water, solvent cointercalation and exchange, cation exchange, polymers, and small molecules, exfoliation, and exfoliated heterostructures, is presented.
Abstract: Layered transition metal oxides are some of the most important materials for high energy and power density electrochemical energy storage, such as batteries and electrochemical capacitors. These oxides can efficiently store charge via intercalation of ions into the interlayer vacant sites of the bulk material. The interlayer can be tuned to modify the electrochemical environment of the intercalating species to allow improved interfacial charge transfer and/or solid-state diffusion. The ability to fine-tune the solid-state environment for energy storage is highly beneficial for the design of layered oxides for specific mechanisms, including multivalent ion intercalation. This review focuses on the benefits as well as the methods for interlayer modification of layered oxides, which include the presence of structural water, solvent cointercalation and exchange, cation exchange, polymers, and small molecules, exfoliation, and exfoliated heterostructures. These methods are an important design tool for further development of layered oxides for electrochemical energy storage applications.
66 citations
TL;DR: In this article, the structural aspects of the crystallographic shear planes and the resulting thermoelectric properties of transition metal oxides with adaptive structures have been investigated with respect to their thermal properties.
Abstract: Thermoelectric devices can help to tackle future challenges in the energy sector through the conversion of waste heat directly into usable electric energy. For a wide applicability low-cost materials with reasonable thermoelectric performances and cost-efficient preparation techniques are required. In this context metal oxides are an interesting class of materials because of their inherent high-temperature stability and relative high sustainability. Their thermoelectric performance, however, needs to be improved for wide application. Compounds with adaptive structures are a very interesting class of materials. A slight reduction of early transition metal oxides generates electrons as charge carriers and crystallographic shear planes as structure motif. The crystallographic shear planes lead to a reduction of intrinsic thermal conductivity. At the same time, the electronic transport properties can be tuned by the degree of reduction. So far only a few transition metal oxides with adaptive structures have been investigated with respect to their thermoelectric properties, leaving much room for improvement. This review gives an overview of thermoelectric oxides, highlights the structural aspects of the crystallographic shear planes and the resulting thermoelectric properties.
50 citations
References
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IBM1
TL;DR: In this paper, Ba−La−Cu−O system, with the composition BaxLa5−xCu5O5(3−y) have been prepared in polycrystalline form, and samples with x=1 and 0.75,y>0, annealed below 900°C under reducing conditions, consist of three phases, one of them a perovskite-like mixed-valent copper compound.
Abstract: Metallic, oxygen-deficient compounds in the Ba−La−Cu−O system, with the composition BaxLa5−xCu5O5(3−y) have been prepared in polycrystalline form. Samples withx=1 and 0.75,y>0, annealed below 900°C under reducing conditions, consist of three phases, one of them a perovskite-like mixed-valent copper compound. Upon cooling, the samples show a linear decrease in resistivity, then an approximately logarithmic increase, interpreted as a beginning of localization. Finally an abrupt decrease by up to three orders of magnitude occurs, reminiscent of the onset of percolative superconductivity. The highest onset temperature is observed in the 30 K range. It is markedly reduced by high current densities. Thus, it results partially from the percolative nature, bute possibly also from 2D superconducting fluctuations of double perovskite layers of one of the phases present.
10,272 citations
TL;DR: In this paper, an ambient temperature rechargeable magnesium battery based on organic electrolytes and positive electrodes capable of reversible intercalation of Mg+2 ions is discussed. But the number of combinations of solvent, solute, and inter-calation cathode which give reasonable battery performance is much more limited for Mg than for alkali metals.
Abstract: Research leading to the construction of an ambient temperature rechargeable magnesium battery based on organic electrolytes and positive electrodes capable of reversible intercalation of Mg+2 ions is discussed. The number of combinations of solvent, solute, and intercalation cathode which give reasonable battery performance is much more limited for Mg than for alkali metals. The only electrolytes which allowed Mg dissolution and deposition were solutions of organomagnesium compounds in ethers or tertiary amines; many of these were unstable in the presence of transition metal oxides or sulfides which were found to function acceptably as intercalation electrodes. Possible directions for future research which could solve these problems are discussed, as well as theoretical aspects of magnesium compound behavior in nonaqueous solvents.
578 citations
427 citations
TL;DR: The physical and structural properties relevant to the ability of transition metal oxides with framework structures to topochemically incorporate lithium are discussed, and Perovskite-related structures are particularly attractive hosts for lithium.
Abstract: A new class of electrode materials for high energy density, rechargeable batteries based on topochemical reactions of lithium and transition metal compounds is evolving. The physical and structural properties relevant to the ability of transition metal oxides with framework structures to topochemically incorporate lithium are discussed. Perovskite-related structures are particularly attractive hosts for lithium.
365 citations
TL;DR: In this paper, the suppression by electric fields of longitudinal resistivity anomalies at 145 and 59 K in the compound Nb${\mathrm{Se}}_{3} was reported, and attributed the observed suppression to Zener breakdown across extremely small gaps introduced by the presence of charge density waves.
Abstract: We report the suppression by electric fields of longitudinal resistivity anomalies at 145 and 59 K in the compound Nb${\mathrm{Se}}_{3}$. Sample resistance was determined by conventional four-probe dc measurement as well as with short current pulses. We attribute the observed suppression to Zener breakdown across extremely small gaps introduced by the presence of charge density waves.
342 citations