Raman study of fractal voids in hot-pressed SiO2

The sensitivity of the dynamic (vibrational) properties of fractal nanocrac ks in hot-pressed silica to the thermal and mechanical prehistory of the ma terial was studied by low-frequency Raman scattering. Samples were prepared from gel-derived and fused powdery products. The Raman data demonstrate th e fractality of elementary continuity defects. From the frequency dependenc e of the Raman intensity, the values of the fracton (spectral) dimension th at reflects the mid-range order in glass, and the dimensions of fractals in real space were calculated. (C) 2001 Elsevier Science B.V. All rights rese rved.