Grinding effect of powder on thermal expansion of silica glass powder compacts

A thermal expansion ten times larger than that of silica glass was observed for the pressed compacts of silica glass powder, which was ground with a planetary pot mill. The extent of the thermal expansion increased with increasing the grinding time. Since quartz powder compacts did not undergo much thermal expansion after grinding, such a large thermal expansion behavior of the silica glass powders seemed to be unique for the silica glass. Solid state Si-29 NMR and IR spectra showed a reduction in the Si-O-Si bonding angle, which resulted due to a distortion of the silica glass network.