Topic
Molybdite
About: Molybdite is a research topic. Over the lifetime, 35 publications have been published within this topic receiving 485 citations. The topic is also known as: MoO3.
Papers
TL;DR: In this paper, a comparative evaluation of the March model and the generalized spherical harmonic was performed with X-ray powder diffraction data for molybdite (MoO3) and calcite (CaCO3) powders uniaxially pressed at five different pressures.
Abstract: Preferred crystallographic orientation, i.e. texture in crystalline materials powder diffraction data, can cause serious systematic errors in phase composition analysis and also in crystal structure determination. The March model [Dollase (1986). J. Appl. Cryst. 19, 267–272] has been used widely in Rietveld refinement for correcting powder diffraction intensities with respect to the effects of preferred orientation. In the present study, a comparative evaluation of the March model and the generalized spherical harmonic [Von Dreele (1997). J. Appl. Cryst. 30, 517–525] description for preferred orientation was performed with X-ray powder diffraction data for molybdite (MoO3) and calcite (CaCO3) powders uniaxially pressed at five different pressures. Additional molybdite and calcite powders, to which 50% by weight silica gel had been added, were prepared to extend the range of preferred orientations considered. The patterns were analyzed initially assuming random orientation of the crystallites and subsequently the March model was used to correct the preferred orientation. The refinement results were compared with parallel refinements conducted with the generalized spherical harmonic [Sitepu (2002). J. Appl. Cryst. 35, 274–277]. The results obtained show that the generalized spherical harmonic description generally provided superior figures-of-merit compared with the March model results.
117 citations
TL;DR: In this article, the mathematics of two commonly used models for preferred orientation (the March-Dollase and the generalized sphericalharmonic models) are reviewed and applied individually to neutron powder data from uniaxially pressed molybdite and calcite powders in Rietveld analyses, as well as the as-received powders.
Abstract: Preferred orientation or texture is a common feature of experimental powder patterns. The mathematics of two commonly used models for preferred orientation—the March-Dollase and the generalized spherical-harmonic models—is reviewed. Both models were applied individually to neutron powder data from uniaxially pressed molybdite (MoO 3 ) and calcite (CaCO 3 ) powders in Rietveld analyses, as well as the as-received powders. The structural refinement results are compared to single-crystal structures. The results indicate that reasonable refinement of crystal structures can be obtained using either the March model or generalized spherical-harmonic description. However, the generalized spherical-harmonic description provided better Rietveld fits than the March model for the molybdite and calcite. Therefore, the generalized spherical-harmonic description is recommended for correction of preferred orientation in neutron diffraction analysis for both crystal structure refinement and phase composition analysis. Subsequently, the generalized spherical-harmonic description is extended to crystal structure refinement of annealed and the aged polycrystalline Ni-rich Ni 50.7 Ti 49.30 shape memory alloys.
112 citations
TL;DR: In this article, it was shown that α-MoO3 is electrochemically active in a calcium cell with nonaqueous electrolyte and the mechanism of intercalation has been explored by using XRD, Raman, and XPS.
Abstract: Calcium batteries could be an alternative to lithium analogues, but this technology is still in its infancy. It is previously known that layered-type molybdite (α-MoO3) can intercalate hydrated calcium ions in aqueous electrolyte, and this intercalation process increases the interlayer spacing. In this work, we have found that α-MoO3 is electrochemically active in calcium cell with nonaqueous electrolyte. The mechanism of intercalation has been explored by using XRD, Raman, and XPS. The layered structure of α-MoO3 is preserved upon electrochemical intercalation of unsolvated calcium, and the perovskite-type structure of CaMoO3 is not formed. The experimental length of the lattice parameter perpendicular to the slab increases from 13.85 to 14.07 A in the first stages of intercalation. This limited increase can be optimum for achieving good electrochemical cycling. The model for calcium intercalation in the interlayer space was optimized by theoretical calculations based on the density functional theory. Th...
74 citations
1 Jan 2005
TL;DR: In this article, a comparative evaluation of the March model and the generalized spherical harmonic was performed with X-ray powder diffraction data for molybdite (MoO3) and calcite (CaCO3) powders uniaxially pressed at five different pressures.
Abstract: Preferred crystallographic orientation, i.e. texture in crystalline materials powder diffraction data, can cause serious systematic errors in phase composition analysis and also in crystal structure determination. The March model [Dollase (1986). J. Appl. Cryst. 19, 267–272] has been used widely in Rietveld refinement for correcting powder diffraction intensities with respect to the effects of preferred orientation. In the present study, a comparative evaluation of the March model and the generalized spherical harmonic [Von Dreele (1997). J. Appl. Cryst. 30, 517–525] description for preferred orientation was performed with X-ray powder diffraction data for molybdite (MoO3) and calcite (CaCO3) powders uniaxially pressed at five different pressures. Additional molybdite and calcite powders, to which 50% by weight silica gel had been added, were prepared to extend the range of preferred orientations considered. The patterns were analyzed initially assuming random orientation of the crystallites and subsequently the March model was used to correct the preferred orientation. The refinement results were compared with parallel refinements conducted with the generalized spherical harmonic [Sitepu (2002). J. Appl. Cryst. 35, 274–277]. The results obtained show that the generalized spherical harmonic description generally provided superior figures-of-merit compared with the March model results.
65 citations
TL;DR: In this paper, the synthesis of molybdenum trioxide nanoribbons assembled into self-standing films is described, and the set of conditions to obtain well-aligned single crystalline, single-phase products was determined; under these conditions it is possible to obtain assemblies of crystals of several centimeters, aligned along a single crystaline direction.
Abstract: In this article we report the synthesis of molybdenum trioxide nanoribbons assembled into self-standing films. The molybdenum oxide crystals are prepared by acid decomposition of sodium molybdate under hydrothermal conditions. The set of conditions to obtain well-aligned single crystalline, single-phase products was determined; under these conditions it is possible to obtain assemblies of crystals of several centimeters, aligned along a single crystalline direction. These crystals are also suitable precursors to other molybdenum chalcogenides, as we present a nanostructured molybdenum sulfide obtained by the sulfidation of these molybdenum oxide nanoribbons. A considerable amount of single nanowires and nanoplatelets of molybdenum sulfide were observed in this material.
35 citations
Related Topics (5)
Performance Metrics
| Year | Papers |
|---|---|
| 2021 | 1 |
| 2020 | 1 |
| 2018 | 4 |
| 2017 | 1 |
| 2015 | 1 |
| 2013 | 2 |