Synthesis and characterization of metastable transition metal oxides and oxide nitrides

Abstract

New routes to vanadium sesquioxide and tantalum oxide nitride (γ-and δ-phase) are presented. Phase pure V 2 O 3 with bixbyite-type structure, a metastable polymorph, was obtained from vanadium fluoride hydrates at ~750 K. It crystallizes in the cubic crystal system in space group Ia3 ̅ with lattice parameter a = 939.30(5) pm. The catalytical properties of the corresponding oxide nitride phases and their oxidation and reduction solid-state kinetics were investigated. The preparation of γ-TaON as a phase pure sample can be realized by ammonolysis of X-ray amorphous tantalum oxide precursors at 1073 K. This metastable tantalum oxide nitride crystallizes in the monoclinic VO 2 (B)-type structure in space group C2/m. The same precursors can be used to synthesize the δ-modification with an anatase-type structure at 1023 K. It crystallizes in the tetragonal crystal system in space group I4 1 /amd. A maximum yield of 82 m % could be obtained. The fundamental band gaps of the synthesized and of other metastable TaON polymorphs were calculated from first principles using the GW method. The present results are compared to experimental data and to previous calculations at hybrid DFT level.

Selective kinetic growth and role of local coordination in forming Al2TiO5-based coatings at lower temperatures

“…49,50 Rather than relying solely on the diffusion of the elements, these techniques may carry an extra degree of freedom by allowing atomic-scale control of the synthesised material through a series of step-wise polycondensations, 42,51 targeted metatheses, 37,38 and ligand reactions. 44 This added flexibility enables the adaption of functional inorganic materials not merely from their elemental compositions but also through their local short-range features, 52,53 such as coordination environments, 54 bonding characteristics and presence of (ordered) vacancies. 55,56 These features characterise many transition metal oxides, showing extensive polymorphism in the metastable domain.…”

Complex of Tris(Phenanthroline)Cobalt(II)Trifluoroacetate: Characterisation and Powder XRD Analysis

“…Therefore, discussing the cell parameters through other simple method by powder X-ray diffraction may be relevant. Quite recently, the cell parameters of some complexes have been estimated from the corresponding powder-XRD by applying Le Bail method [9][10][11][12][13][14] , which is usually applied for powder metal oxides [15][16][17][18] . While in the absence of single crystal due to unsuccessful on producing them are quite often, the powder XRD offers an alternative way to estimate the cell parameters, and probably the position of atoms and thus bond lengths as well as bond angles might be depicted in one occation.…”

Preparation, Electronic Properties, and Powder-XRD Structure Analysis of 3,5-Bis(pyridin-2-yl)-H-1,2,4-triazoledichloridocopper(II)

“…This is quite common for the oxides compounds following Rietveld method [e.g. [25][26][27]. However, it has been applied to that of iron(II) complex [28] quite recently and found to be a significant result.…”