Void structure in silica glass with different fictive temperatures observed with positron annihilation lifetime spectroscopy

We examine voids in silica glasses with different fictive temperatures using positron annihilation lifetime spectroscopy. The pick-off annihilation lifetime of ortho-positronium increases with the fictive temperature, T-f, indicating that the void size increases. High T-f leads to high density and low degree of network polymerization so that increasing void size means that the density fluctuation of the silica glass increases with high T-f. Assuming that such density fluctuation causes light scattering, the previously reported T-f dependence of the Rayleigh scattering coefficient can be well explained by the change in void size. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4761982]