Nuclear quadrupole resonance spectra of drawing-induced crystallization in As2Se3 fibers

Pulsed As-75 nuclear quadrupole resonance (NQR) experiments performed on fibers of As2Se3 drawn at various rates (> 100 m/min) reveal structural changes from the bulk, well-annealed glass. In addition to the presence of As-As bonds in the nominally stoichiometric fibers, a distorted crystalline phase (< 10% by volume) occurs at the largest draw rates. Because they are highly distorted, these crystallites are not observable by X-ray diffraction spectroscopy in almost all cases. On the other hand, the NQR experiments show these crystalline regions very clearly as small width components in the NQR spectra between 56 and 60 MHz. In addition to being strained, the imbedded crystallites are dominated by surface effects because they partially revert to the amorphous phase over time when stored at 300 K. The nature of the distortions in these crystallites and the kinetics of this counter-intuitive annealing behavior are not well determined. Because large draw rates are important in commercial production of fibers, the drawing-induced crystallization in this prototypical chalcogenide glass may have implications for the use of these materials in infrared transmission applications. (C) 1997 Elsevier Science B.V.