Influence of impurities on quality of quartz glass

The results show that the characteristics of the raw materials affecting the quality of quartz glass mainly include the types and contents of impurities and gases, and the particle size distribution of the powders.

In the high temperature (>1000℃), impurity ions li+, K +, +, +, $number, $literal, etc. will induce SiO2 glass precipitation crystals. Alkali metal impurities will also reduce the melting point of quartz raw materials and softening points. The transition element affects the optical transmittance of the quartz glass. Aluminum is the main impurity element, a small amount of aluminum will not affect the appearance of quartz glass quality, but it is not conducive to reduce radiation resistance.

The gases in the raw material are mainly from the surface moisture of the powder and the components in the mineral gas-liquid inclusions. In the fused quartz glass, the SiO2 melt viscosity is high, including the gas is not easy to exclude, but grew into a bubble, affecting the quality of quartz glass. The smaller the gas molecule, the greater the diffusion coefficient, such as he, H2, the diffusion coefficient is large, easy to expel [3]. N2, CO, CO2, CXHX and other gases are very difficult to discharge from the melt, eventually forming bubbles, affecting the transparency of quartz glass.

In the melting process of quartz powder, because of the difference of the surface activation energy, small particles are melted first than large particles. The fused quartz will cover the surface of the fused quartz particles, causing the bubbles to not be ruled out. Small particle clearance contains a large amount of gas, will increase the exhaust difficulty. Coarse-grained quartz is not easy to melt completely, resulting in uneven glass. The actual particle size depends on the preparation process of quartz glass.