| Sapphire is an ideal, multispectral and broadband window material. In comparison with general broadband window material, it has excellent optical, mechanical properties and chemical stability, high strength, high hardness and resistance to erosion, not only it has the merit of wind and wear resistance, but also has good electrical insulation and heat conductivity. It can work well in close to 2000℃. The size of window materials for many modern optical systems far exceeds the maximum sapphire grown by EFG method. The another way to obtain larger sizes sapphire window is connect two or more sapphire. In this paper, the diffusion bonding were used for the joining of sapphire and the Intermediate solder use the alumina ceramic substrate made by tape casting.Effects of fabrication technical parameters on slurry properties were studied, and the best technical parameters were decided as: first milling time is 12h, second milling time is 24h. Effects of pH and the components of additive on slurry viscosity were studied. It was found that when pH was 9 and the content of PAA was 0.5wt% of the slurry, the content of PVA was 4.5wt% of the slurry, the weighty ratio of PVA to PEG were 1:0.7, the surface smooth tapes with enough and flexible and organization uniformly were produced.The Al2O3 ceramic substrates made by tape casting were used to carry out the duffusion bonding sapphire as the middle layer. Effects of diffusion bonding technical parameters on the joint microstructure and joining property were studied. Besides, we analyzed the fracture behavior of joint by various methods of analysis and testing, such as SEM, EDS, etc. Through above-mentioned research, the best duffusion bonding sapphire technical parameters were decided as: bonding temperature was 1650℃, the pressure 30MPa, holding time 180min, the optimal thickness of the middle layer was 0.2mm. In this processing parameters, we got the best diffusion bonding results, the maximum joining strength reached 266MPa...
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