Low-frequency Raman scattering and small-angle X-ray scattering of glassesinclined to phase decomposition

Low-frequency (<1000 cm(-1)) Raman scattering of lithium aluminosilicate (1 2Li(2)O : 15Al(2)O(3) : 73SiO(2) with 4 mol% TiO2) glasses with addition of titanium dioxide has been studied. With a heat treatment at temperatures 6 60 degrees C, 700 degrees C, 720 degrees C and 820 degrees C and for variou s times and sequences of temperature, our samples decompose into nanometer sized dispersed aluminotitanate particles. In Raman spectra of these glasse s an evolution of a boson peak was observed. The width of the relatively br oad boson band decreases as does the frequency of the band. From small-angl e X-ray scattering data we conclude that the boson peak is connected with e lastic vibrations of amorphous or crystalline regions of inhomogeneity with a dimension of similar to 1.7 nm in initial glasses or larger depending on the heat treatment sequences. (C) 1999 Elsevier Science B.V. All rights re served.