Identification of tungstic and molybdic “acids” by X-ray powder diffraction

Freedman, Meyer L.; Leber, S.

doi:10.1016/0022-5088(64)90039-6

Cited by 20 publications

(7 citation statements)

References 6 publications

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“…However, the hydration depends on the washing and drying conditions. Several authors employed a similar precipitation reaction to prepare WO 3 ·2H 2 O. − So far, to the best of our knowledge, the layered WO 3 ·1.3H 2 O (≡ 1/2H 2 W 2 O 7 ·1.6H 2 O) was not prepared by a simple precipitation reaction using Na 2 WO 4 , SrCl 2 , and HCl. The EDX analysis shows peaks due to W in the as-prepared WO 3 ·2H 2 O and WO 3 ·1.3H 2 O, and no peaks due to Na, Sr, and Cl atoms were observed (see Supporting Information Figures S1 and S2).…”

Section: Resultsmentioning

confidence: 99%

“…The chemistry of tungsten trioxide hydrates (TTHs), also well-known as tungstic acids, has been studied since the early 1900s. − Several different chemical compositions, crystal structures, and microstructures were identified for WO 3 · n H 2 O ( n = 0, 0.33, 0.5, 1, and 2). ,, The water content in the TTHs appears to be very crucial in the stabilization of different types of crystal structures. For example, WO 3 ·2H 2 O exhibits a layered structure (space group P 2 1 / n ; a = 10.4840(43) Å; b = 13.8041(56) Å; c = 10.5733(43) Å; β = 91.0418(2)°), which consists of a corner-sharing single-sheet of WO 5 (OH 2 ), and the second water molecule is occupied between the interlayers (Figure a).…”

Section: Introductionmentioning

confidence: 99%

“…The chemistry of tungsten trioxide hydrates (TTHs), also well-known as tungstic acids, has been studied since the early 1900s. [1][2][3] Several different chemical compositions, crystal structures, and microstructures were identified for WO 3 3 nH 2 O (n = 0, 0.33, 0.5, 1, and 2). 1,3,4 The water content in the TTHs appears to be very crucial in the stabilization of different types of crystal structures.…”

Section: Introductionmentioning

confidence: 99%

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Revisiting Tungsten Trioxide Hydrates (TTHs) Synthesis - Is There Anything New?

2009

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We report a very simple precipitation route to prepare a layered perovskite-type structure, tungsten trioxide hydrate (TTH), with the nominal chemical formula of WO(3) x 1.3 H(2)O (identical with 1/2H(2)W(2)O(7) x 1.6 H(2)O), using aqueous Na(2)WO(4) and SrCl(2). Our investigation shows that the concentration of HCl used to dissolve the SrCl(2) plays a crucial role in the stabilization of different structure types of layered TTHs. Highly acidic SrCl(2) (dissolved in 9 M HCl) solution yields an orthorhombic layered TTH of WO(3) x 2 H(2)O, while SrCl(2) dissolved in 3 M HCl appears to give an A-site-deficient Ruddlesdon-Popper (RP) related double-perovskite-type layered structure (DOLS-TTH). A well-known scheelite-type structure is obtained under weakly basic conditions (pH = 10.3 for Na(2)WO(4(aq)), 7.0 for SrCl(2(aq))). Previously, RP-type a DOLS of H(2)W(2)O(7) x 0.58 H(2)O was prepared, using an acid-leaching method, from the corresponding n = 2 member of the layered Aurivillius phase (AP) Bi(2)W(2)O(9). Powder X-ray diffraction showed the formation of layered RP DOLS with a large d spacing approximately 12.5 A, which is consistent with acid-leaching (Kuto et al. Inorg. Chem. 2003, 42, 4479-4484; Wang et al. J. Solid State Chem. 2007, 180, 1125-1129) and exfoliation (Schaak et al. Chem. Commun. 2002, 706-707) methods for synthesized TTHs. The proposed DOLS-TTH structure of newly prepared TTHs was further confirmed by an intercalation reaction using n-octylamine (C8A). A transmission electron microscopy study showed the formation of nanosized particles, and scanning electron microscopy coupled with energy dispersive X-ray analysis showed the absence of Na and Sr in the air-dried, as-precipitated products under acidic conditions. The bulk electrical (proton) conductivity of presently prepared TTHs was found to be on the order of 10(-4)-10(-3) S/cm at room temperature in wet N(2).

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Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Revisiting Tungsten Trioxide Hydrates (TTHs) Synthesis - Is There Anything New?

2009

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“…In our first work, the WO 3 ·H 2 O powder was synthesized according to the Freedman method, , which is based on a rapid precipitation of the product. According to this route, WO 3 ·2H 2 O precipitate is obtained by progressively adding a 1 M Na 2 WO 4 ·2H 2 O solution (50 mL) to a 3 M HCl solution (450 mL) at 25 °C.…”

Section: Methodsmentioning

confidence: 99%

Control of Powder Microstructure for Improved Infrared Reflectance Modulation of an Electrochromic Plastic Device

et al. 2003

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The so-called plastic technology first developed for Li-ion batteries is demonstrated for its potential optical applications in infrared emissivity control. WO 3 ‚H 2 O powder embedded in a plastic matrix is used as the active component in the LiCoO 2 /Li electrolyte/WO 3 ‚H 2 O system. The role of the microstructure of WO 3 ‚H 2 O as an electrochromic material is investigated. For instance, platelet-shaped grains with a surface area as large as 15 µm 2 induce a large improvement in device contrast properties. Reflectance measurements show a 53% contrast between the bleached and colored states over the 8-12 µm range. This effect is likely rooted in the free electron mobility in addition to scattering and phonon effects. The optical modulation performance over the range 2.5-20 µm compares favorably with literature results on solid devices built from annealed and sputtered m-WO 3 thin films.

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“…Several tungstic acids (alternatively referred to as tungsten trioxide hydrates) with different compositions and structures have been identified. One of these, WO 3 ·2H 2 O, − which is isostructural with MoO 3 ·2H 2 O, consists of single sheets of corner-sharing WO 5 (OH 2 ) octahedra and interlayer water .…”

Section: Introductionmentioning

confidence: 99%

A Layered Tungstic Acid H₂W₂O₇·nH₂O with a Double-Octahedral Sheet Structure: Conversion Process from an Aurivillius Phase Bi₂W₂O₉ and Structural Characterization

et al. 2003

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The conversion process of an Aurivillius phase, Bi(2)W(2)O(9), into a layered tungstic acid by hydrochloric acid treatment has been investigated, and resultant H(2)W(2)O(7) x nH(2)O has been fully characterized. The c parameter of Bi(2)W(2)O(9) [2.37063(5) nm] decreases to 2.21(1) nm in an acid-treated product dried at ambient temperature. The a and b parameters of Bi(2)W(2)O(9) [a = 0.54377(1) nm and b = 0.54166(1) nm] also decrease slightly to a = 0.524(1) nm and b = 0.513(1) nm in the acid-treated product dried at ambient temperature, indicating structural changes in the ReO(3)-like slabs in Bi(2)W(2)O(9) upon acid treatment. Drying at 120 degrees C leads to a further decrease in the c parameter [1.86(1) nm] with no notable change in the a and b parameters [a = 0.5249(2) nm and b = 0.513(2) nm]. The formation of an expandable layered structure is demonstrated by the successful intercalation of n-octylamine [interlayer distance 2.597(9) nm] and n-dodecylamine [interlayer distance 3.56(2) nm]. The compositions of the acid-treated products are determined to be H(2)W(2)O(7) x nH(2)O typically with n = 0.58 for the air-dried product and n = 0 for the product dried at 120 degrees C. As a consequence, the composition of the layer is H(2)W(2)O(7), and the decrease in the c parameter upon drying is ascribable to the loss of interlayer water. Scanning electron microscopy reveals no morphological change during acid treatment, which strongly suggests a selective leaching of the bismuth oxide sheets as a reaction mechanism. High-resolution transmission electron microscopy (HREM) observation of the acid-treated product shows consistency with a structural model for H(2)W(2)O(7), derived from Bi(2)W(2)O(9) through removal of the bismuth oxide sheets and contraction along the c axis. HREM observation also reveals that the WO(6) octahedra arrangement changes slightly with acid treatment. A one-dimensional electron density map projected on the c axis for the product dried at 120 degrees C, H(2)W(2)O(7), shows good consistency with that calculated for the structural model.

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Identification of tungstic and molybdic “acids” by X-ray powder diffraction

Cited by 20 publications

References 6 publications

Revisiting Tungsten Trioxide Hydrates (TTHs) Synthesis - Is There Anything New?

Revisiting Tungsten Trioxide Hydrates (TTHs) Synthesis - Is There Anything New?

Control of Powder Microstructure for Improved Infrared Reflectance Modulation of an Electrochromic Plastic Device

A Layered Tungstic Acid H₂W₂O₇·nH₂O with a Double-Octahedral Sheet Structure: Conversion Process from an Aurivillius Phase Bi₂W₂O₉ and Structural Characterization

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Identification of tungstic and molybdic “acids” by X-ray powder diffraction

Cited by 20 publications

References 6 publications

Revisiting Tungsten Trioxide Hydrates (TTHs) Synthesis - Is There Anything New?

Revisiting Tungsten Trioxide Hydrates (TTHs) Synthesis - Is There Anything New?

Control of Powder Microstructure for Improved Infrared Reflectance Modulation of an Electrochromic Plastic Device

A Layered Tungstic Acid H2W2O7·nH2O with a Double-Octahedral Sheet Structure: Conversion Process from an Aurivillius Phase Bi2W2O9 and Structural Characterization

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A Layered Tungstic Acid H₂W₂O₇·nH₂O with a Double-Octahedral Sheet Structure: Conversion Process from an Aurivillius Phase Bi₂W₂O₉ and Structural Characterization