The structure of fused silica glass is relaxed, allowing the diffusion of ions of certain gases through its network at high temperatures, among which sodium ion diffusion is relatively fast.
This property of fused silica glass is of great importance to users. For instance, when fused silica glass is used as high-temperature containers or diffusion tubes in the semiconductor industry, semiconductor materials demand extremely high purity. Therefore, the refractory materials used as furnace linings that come into contact with fused silica glass must undergo high-temperature and cleaning treatment in advance to remove alkaline impurities such as potassium and sodium before being placed inside the fused silica glass for use.
At room temperature, fused silica glass can be regarded as impermeable to gases. Even at high temperatures (e.g., 700℃), the permeability constants of certain gases are very small. Hence, it can be applied in high-temperature and high-vacuum equipment.