LIF-FILM-ASSISTED DIFFUSION BONDING OF MGF2 CERAMICS

The joining of MgF by hot pressing was studied. A layer of LiF with 10-12-mu-m thickness was used as agent to decrease the bonding temperature and to avoid breaching. The main factors that influenced the light scattering loss were the abnormal grain growth and voids in the interlayer, near-layer and matrix regions. Parameters of 550-degrees-C for 5 h and 575-degrees-C for 3 h under a loading pressure of 300 kgf cm-2 were the best conditions for obtaining high transmittance. High transmittance was related to the preferred orientation of the LiF film (011BAR) and slower grain growth. According to the grain growth, the value of the light scattering efficiency factor was calculated as 1.9308 which is independent of the wavelength of the incident light and of the layer region of the samples. Increasing the loading pressure to 430 kgf cm-2 could improve the relative transmittance by about 10% and 40% for bonding at 650-degrees-C for 3 h and 700-degrees-C for 3 h respectively, and for the other samples the transmittance was lowered by refining the grain size via the recrystallization process.