Structural changes of SiO₂ glass by mechanical milling

Abstract

Structural changes of ground SiO₂ glass were investigated using X-ray diffraction (XRD), Fourier transform infrared (FT-IR) spectroscopy, and Raman spectroscopy. SiO₂ glass samples were ground in a ball mill for up to 500 h. Reduction in the particle size of ground SiO₂ glass samples was observed up to ∼ 80 h of milling. After 80 h of milling, the particle size of ground SiO₂ glass remained almost constant at approximately 3 μm. The first sharp diffraction peak (FSDP) position (q₁) of the XRD pattern for ground SiO₂ glass shifted from 1.500 (original) to 1.544 (500 h of milling) Å^-1. The variation may be attributed to a change of the intermediate-range structure. The FSDP position of the 500 h ground SiO₂ glass returned to the original value after annealing at 1000 °C. This annealing behavior includes two components. The variation in q₁ for annealing up to ∼ 500 °C is small (0.0087 Å^-1) and may be attributed to an increase of the Si-O-Si angle. However, for annealing at 500-1000 °C, a large variation was observed (0.0350 Å^-1) and it may be attributed to a decrease of 3-membered rings. IR spectra of samples milled up to ∼ 80 h revealed sharpening of the ν = 1100 cm^-1 band (Si-O stretching mode) and a decrease in the absorption of the ν = 800 cm^-1 band (Si-O-Si bending mode). The IR analyses indicate the shrinkage of Si-O-Si linkages by milling. For over 80 h of milling, these variations are small. The particle size remains almost constant for over 80 h of milling, and therefore, only structural changes in a particle would be responsible for the changes in the IR spectra. The Raman spectra exhibited an increase in the luminescence intensity for milling up to ∼ 40 h. The luminescence may result from surface defect structures on SiO₂ glass grains, and the increase in the luminescence intensity is consistent with particle size reduction by milling.