Structural study of ammonium metatungstate

Christian, Joel B.; Whittingham, M. Stanley

doi:10.1016/j.jssc.2008.03.034

Cited by 29 publications

(22 citation statements)

References 26 publications

(28 reference statements)

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“…The XRD spectrum of AMT1 does not resemble to any of the published XRD data about AMT [37,38] or the available XRD reference cards of AMT (PDF 00-039-0168 and 04-012-6600). Thus, using Si internal standard we determined the cell parameters of our AMT sample, and refined them with full profile fit.…”

Section: Characterization Of Amt1mentioning

confidence: 83%

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Structure and thermal decomposition of ammonium metatungstate

Hunyadi

Sajó

Szilágyi

2013

J Therm Anal Calorim

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The structure, morphology of ammonium metatungstate (AMT), (NH 4 formed between 380-500 °C, (iv) which then transformed into the more stable m-WO 3 between 500-600 °C. As a difference in air, the as-formed NH 3 ignited with an exothermic heat effect, and nitrous oxides formed as combustion products. The thermal behavior of AMT was similar to ammonium paratungstate (APT), (NH 4 ) 10 [H 2 W 12 O 42 ]•4H 2 O, the only main difference being the lack of dry NH 3 evolution between 170-240 °C in the case of AMT.)

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Section: Characterization Of Amt1mentioning

confidence: 83%

“…According to Christian and Wittingham [37] as well as Fait et al [38], depending on its crystal water content AMT can have three different cubic unit cells, however, only of them, the AMT•22H 2 O has an XRD reference card (PDF 00-039-0168). There exists a fourth, anorthic AMT structure (PDF 04-012-6600) as well.…”

Section: Introductionmentioning

confidence: 99%

Structure and thermal decomposition of ammonium metatungstate

Hunyadi

Sajó

Szilágyi

2013

J Therm Anal Calorim

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“…[1][2][3] In addition, there are several polyoxometalates (POMs)  discrete nanocluster anions constructed of W(VI) and oxygen. [4][5][6] POMs are usually comprised of W, Mo or V, and O, which form cyclic geometries resulting in macromolecular clusters. 7 There are many variations of such discrete entities, especially because of the transition metals' mixed-valence characteristics.…”

Section: Introductionmentioning

confidence: 99%

“…The decatungstate anion [W10O32] 4-, the paratungstate anion [H2W12O42] 10-and the metatungstate anion [H2W12O40] 6-(the latter may also be described in the literature as the dodecatungstate 5 , dihydrogendodecatungstate 8 or metadodecatungstate 8 anion) are examples of these arrangements. The two protons of the [H2W12O40] 6anion are located within the central cavity of the Keggin-like structure and are relatively inaccessible.…”

Section: Introductionmentioning

confidence: 99%

Thermal stability of mesoscopic compounds of cetyltrimethylammonium and Keggin metatungstates

et al. 2017

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A hybrid surfactant/polyoxometalate compound was synthesized by combining isopolytungstate anions with the cationic surfactant cetyltrimethylammonium bromide (CTA-Br) to produce a hierarchical compound that we identify as (CTA)[HWO]Cl·2HO. At room temperature the compound consisted of hexagonally ordered sheets of Keggin ions, with an intervening gallery containing alkyl-chains of the organic cations. The synthesis was highly dependent on solution pH, reaction time and the order in which the reactants were added. We examined the effect of temperature on the stability of (CTA)[HWO]Cl·2HO using thermal gravimetric analysis, differential scanning calorimetry, FT-IR spectroscopy and in situ synchrotron X-ray diffraction, and found a step-wise conversion to monoclinic WOvia a series of intermediates. Heating under nitrogen atmospheres accelerated transition events by ∼100 °C when compared to heating in air. During heating, the interplanar gallery at first expanded in a series of steps starting at 90 °C as the CTA amphiphiles changed orientation, before collapsing rapidly at 240 °C, a temperature coinciding with the removal of about 40% of the organic material. Between 240 and 320 °C, the material consisted of fragments of the Keggin ion cores, arranged in 2D hexagonally-packed sheets. At ∼330 °C, the Keggin ions were completely destroyed and replaced by bulk WO which, upon further heating, transformed to bulk WO or WO depending on the environment.

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“…Typically, simple two-body potentials with Coulomb and Lennard-Jones terms served as energy functions; such simple potentials were sufficient because the combination of experimental input and theoretical energy function delivered a high synergy by eliminating many unrealistic local minima on the energy landscape. One up-todate implementation, the program ENDEAVOUR (Putz, 2000), has already been very successful in 'real life' applications, generating convincing structure candidates for such different systems as K 2 CN 2 (Becker & Jansen, 2000), sulfur (Crichton et al, 2001), Na 3 PSO 3 (Pompetzki & Jansen, 2002), Ag 2 NiO 2 (Schreyer & Jansen, 2002), Ag 2 PdO 2 (Schreyer & Jansen, 2001), GaAsO 4 (Santamaría-Pé rez et al, 2006, ammonium metatungstate (Christian & Whittingham, 2008), the zeolite-like structure Na 1Àx Ge 3þz (Beekman et al, 2007), Tl 2 CS 3 (Beck & Benz, 2009) and BiB 3 O 6 (Dinnebier et al, 2009).…”

Section: Structure Determinationmentioning

confidence: 99%

Addressing chemical diversity by employing the energy landscape concept

Jansen¹,

Doll²,

Schön³

2010

Acta Cryst Sect A

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Exploring the structural diversity of a chemical system rests on three pillars. First, there is the global exploration of its energy landscape that allows one to predict which crystalline modifications can exist in a chemical system at a given temperature and pressure. Next, there is the development of new synthesis methods in solid-state chemistry, which require only very low activation energies such that even metastable modifications corresponding, for example, to minima on the landscape surrounded by low barriers can be realized. Finally, there is the theoretical design of optimal synthesis routes, again based on the study of the system's energy landscape. In this paper the energy landscape approach to the prediction of stable and metastable compounds as a function of temperature and pressure is presented, with a particular focus on possible phase transitions. Furthermore, several examples are presented, where such predicted compounds were subsequently successfully synthesized, often employing a newly developed synthesis method, low-temperature atom-beam deposition.

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Structural study of ammonium metatungstate

Cited by 29 publications

References 26 publications

Structure and thermal decomposition of ammonium metatungstate

Structure and thermal decomposition of ammonium metatungstate

Thermal stability of mesoscopic compounds of cetyltrimethylammonium and Keggin metatungstates

Addressing chemical diversity by employing the energy landscape concept

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