MS13-P13 High-Accurate Measurement of Cell Dimensions of Niobium α-phase in Niobium-Oxygen SystemWe observe traceability of high-purity niobium properties in the oxides and chemical bonds of niobium-content chemical compounds minerals and related materials [1-3]. Two approaches for the determining of the structural characteristics of niobium are used. The first variant compares our and different results of X-ray studies of "oxygen-free" niobium using conventional and synchrotron X-Ray methods. After additional annealing of samples in ultra-high vacuum and at high temperatures, the oxygen content in the samples does not exceed 0.03 % mass. The nitrogen concentration is very small 9±1 ppm w, the average content oxygen in these samples is 0.015 ± 0.003% (mass fraction).
The second variant of approach use extrapolates dependence of the unit cell dimension from the oxygen content obtained for samples of the Nb-O system. The impurity content has been estimated by X-ray fluorescence spectrometry on an M1 Mistral analyzer (of Bruker firm). The niobium content is estimated from the measurement results as 99.99% for possible 34 elements. A sample of the alpha-phase of niobium with an oxygen content of about 0.3 wt. % is investigated by single crystal X-ray diffraction. Two complete experiments were performed in the for spherical single, using a detector ССDs, MoKα1-radiation and a wavelength of 0.070932 nm. At room temperature, from 2200 to 2800, the Bragg reflections are collected for the samples in order to fill to maximum the entire Ewald sphere. The spatial group of the unit cell is Im3m (No. 229). The average value of the two experiments of the unit cell dimension (lattice constant) is 0.33062(5) nm. This value is in good agreement with the results of six experiments given in the ICCD PDF-database.
Based on the results of the experiments of the increased accuracy and data from the references, the dependence of the value of the unit cell dimension of niobium on the oxygen content has been plotted. Linear extrapolation to zero value results in a value of а=0.32988(5) nm. This value is in good agreement with the data on unit cell dimension for "oxygen-free" niobium а=0.33005(2) nm. Thus, this dependence can also be used to estimate the oxygen content in various samples of the alpha-phase in the Nb-O system. Such samples with low content of oxygen are used also to create more efficient thermal converters. Thin protective layers of coatings of niobium oxides are also widely used in various spheres of the industry.References:
 Vousden, P. (1951). Acta Crystallographica, 4(4), 373-376.
 Kodess, B. N. (1979). Physics Letters A, 73(1), 53-54.
 Bojko et al. (1972). Kristallografiya, 17(3), 683-685, (in russian).Keywords: high-purity Niobium, system Nb-O, unit cell dimension