MS13-P12 High-Accuracy Measurement of Cell Dimensions of the Vanadium ɑ- and β-phases in V-O System We observe traceability of high-purity vanadium properties in the oxides and chemical bonds of minerals and related materials. High-accuracy measurements using conventional and synchrotron X-Ray methods have been carried out to determine structural characteristics of single crystals zone melting vanadium. The impurity content for possible 34 elements in the investigated crystalline samples was estimated, using an M1 Mistral micro-fluorescence spectrometer (of Bruker firm). The vanadium content was estimated from the measurement results as 99.98%. The oxygen and nitrogen content (mass fraction, %) in the samples was determined using a TС600 analyzer (LECO), by reducive melting in a graphite crucible in an inert gas (helium) flow. The hydrogen content was determined using the RHEN602 analyzer (of LECO firm) by reducive melting in a graphite crucible in an inert gas (argon) flow. The average value of oxygen concentration was 900 ppm w, nitrogen ‒ 200 ppm w, and, importantly, hydrogen was only 40 ppm w. To assess the effect of the purity of single crystals on mechanical properties, Vickers hardness measurements (Hardness tester 930N from Wolpert firm) were performed. The obtained hardness value of 135 HV indicates the acceptable purity of the single crystals used.
Both types of samples ‒ ɑ-phase and β-phase ‒ were investigated using a CCD detectors, MoKα1-radiation, and a wavelength of 0.070932 nm. 1900 to 2500 Bragg reflections were collected for each of the three samples for the ɑ-phase at room temperature, to fill to maximum the entire Ewald sphere. The spatial group of the unit cell is Im-3m (No. 229). The average value of the three experiments of the unit cell dimension (lattice constant) was 0.303465(5) nm. Two similar complete experiments were performed in the same way for spherical single crystals of the vanadium β-phase. At room temperature, from 2200 to 2800, the Bragg reflections are collected. It was found that the value of one of the dimensions of the unit cell of the β-phase was a = 0.30409(2), which was close to the value of the lattice constant of ɑ-phase of vanadium. For the second constant of the tetragonal unit cell, the value was b = 0.3373(5) nm. The latter value noticeably increased because of additional introduction of oxygen into this unit cell. Thus, the use of data on the original elements with a minimum content of oxygen impurities allows to extract and establish the inherited structural features in various vanadium-content chemical compounds and alloys [1-3].
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Keywords: vanadium-oxygen system, unit cell dimension, inherited structural features