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The <i>h</i> -Sb <sub/>x</sub> WO <sub/> 3+2 <i>x</i> </sub> Oxygen Excess Antimony Tungsten Bronze
摘要： The previously unreported oxygen excess hexagonal antimony tungsten bronze is reported, with a composition of Sb0.5W3O10, in the following denoted as h-SbxWO3 + 2x with x = 0.167, to demonstrate its analogy to classical AxWO3 tungsten bronzes. This compound forms in a relatively narrow temperature range between 580 8C < T < 620 8C. It was obtained as a dark-blue polycrystalline powder, and as thin, needle-shaped, blue single crystals. h-SbxWO3 + 2x crystallizes in the hexagonal space group P6/mmm with the cell parameters a = 7.4369(4) (cid:2) and c = 3.7800(2) (cid:2). The antimony and excess oxygen occupy the hexagonal channels within the network of corner-sharing WO6 octahedra. h-SbxWO3 + 2x has a resistivity of 1300 K (cid:2) 1.28 mW cm at room temperature, with little if any temperature-dependence on cooling. DFT calculations on a simplified model for this compound find a metallic-like electronic structure with the Fermi level falling within rather flat bands, especially around the G point.
关键词： hexagonal bipyramids,metallic oxide,tungsten,antimony,bronze
更新于2025-09-23 15:23:52
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Metastable crystalline phase in two-dimensional metallic oxide nanoplates
摘要： Structural phase transition in crystals induced by high-pressure or high-temperature conditions may result in the development of unusual physical and chemical properties; these properties are often difficult to stabilize under ambient conditions. Here we adopted a simple method in which ultrathin cerium oxide nanoplates (< 1.4 nm) were synthesized to increase the surface atomic content, allowing transformation from a face-centered cubic (fcc) phase to a body-centered tetragonal (bct) phase. Three types of cerium oxide nanoparticles of different thicknesses, i.e., 1.2-nm ultrathin nanoplates, 2.2-nm nanoplates, and 5.4-nm nanocubes, were examined using transmission electron microscopy and X-ray diffraction. The metastable bct phase was observed only in ultrathin nanoplates. Thermodynamic energy analysis confirmed that the surface energy of the ultrathin nanoplates is the cause of the remarkable stabilization of the metastable bct phase. The mechanism of surface energy regulation can be expanded to other metallic oxides, thus providing a new means for manipulating and stabilizing novel materials under ambient conditions that otherwise would not be recovered.
关键词： metastable phase,thickness,surface unsaturated coordination ratio,Ultrathin nanoplates,metallic oxide nanoparticles
更新于2025-09-04 15:30:14