Time-Resolved X-ray Powder Diffraction Using a Large-Area CCD-Based Detector and Rietveld Refinement: Solid-State Polymerization of S2N2 to (SN)x

• Published in: Journal of synchrotron radiation 1997-03, Vol.4 (2), p.83-94
• Main Authors: Svensson, S. O., Birch, J., Müller, H., Kvick, Å.
• Format: Article
• Language: English
• Subjects: charge-coupled device detectors; powder diffraction; Rietveld refinement; S2N2; time-resolved studies; X-ray area detectors
• ISSN: 1600-5775; 0909-0495; 1600-5775
• DOI: 10.1107/S0909049597000265

A kinetic study of the solid‐state polymerization of disulfur dinitride (S2N2) to polysulfur nitride [(SN)x] has been performed, combining monochromatic high‐energy (λ = 0.3263 Å) synchrotron radiation X‐ray powder diffraction, a large‐area (ø = 220 mm) CCD‐based X‐ray image‐intensifier detector and Rietveld refinement. Recently developed techniques for detector calibration and reduction of two‐dimensional images to one‐dimensional diffraction patterns have been employed for data processing/analysis. Good fits were obtained after Rietveld refinement [Rp = 8.4%, wRp = 9.4%, sin(θmax)/λ = 0.585 Å−1] of diffraction patterns of S2N2 from images with 2 s exposure time. The solid‐state polymerization of S2N2 to (SN)x, was followed at a maximum rate of two diffraction images per minute. Scale factors and cell parameters for S2N2 and β‐(SN), as functions of time were readily obtained after Rietveld refinement of the diffraction patterns obtained from each individual image throughout the polymerization. The polymerization was preceded by a lattice distortion of S2N2, and at 50% conversion the a axis had decreased by about 1% and the c axis had increased about 1%. The polymerization yielded not only the expected polymer β‐(SN)x, but also a small amount of a compound that could be another phase of (SN)x.