Quantitative phase analysis of boron nitride nanotubes using Rietveld refinement

Crystalline boron nitride nanotubes (BNNTs) with an average outer diameter of about 40 nm and several micrometres in length were synthesized by chemical vapour deposition from boron and magnesium oxide. Rietveld refinement and 11B solid-state nuclear magnetic resonance (NMR) spectroscopy were employed to quantitatively determine the phase of synthesized BNNTs. The structural parameters for the BNNTs were determined by Rietveld refinement against powder x-ray diffraction data with a model based on the results of NMR analysis. The final weighted R-factor, Rwp, was 6.08% and the goodness-of-fit indicator, S (= Rwp/Re), was 1.52. The BNNTs consisted of hexagonal BN, rhombohedral BN and MgO with refined weight fractions of 76.3%, 21.2% and 2.5%, respectively.