Joining Of Si₃N₄Ceramic Using The Interlayer Of β-Sialon-Glass Doped With Different Rare Earth

A joint of Si₃N₄ceramic produced by β-Sialon-glass for middle was obtained.Effect of different atmosphere, joining parameters and type of rare earth onmicrostructure and mechanical properies of joint was investigated. The composition ofeach phase and microstructure in the joint was analysed by the SEM、EDS、XRD andTEM. Then the mechanism of the interface was discussed.In this research, at low temperature solder doped different type of rare earth couldproduce liquid phase at0.1MPa Ar. β-Sialon phase formed in welding seam. Strengthof joint was high. The maximum values of strength reaches248MPa at the temperatureof1650℃for30min by used solder doped Nd rare earth. Silicon nitride ceramicdecomposed. At1MPa atmosphere of N₂the joint had void and craze. The value ofstrength was low. At0.1MPa atmosphere of N₂, the interface bonding of silicon nitridewas well.According to the analysis of microstructure, the joint include three parts: the Si₃N₄ceramic substractes; layer of diffusion and β-Sialon-glass phase in the welding seam.Accroding to the microstructure, the black β-Sialon phase dispersed in the white glass.With increasing the connected temperature, the rate of silicon nitride ceramics dissolvedin seam acceletate when using Nd element solder connected silicon nitride ceramics.The diffusion layer become thick. β-Sialon phase in the seam increased. Effect ofjoining temperature on three points bonding strength has a peak. With increasingholding time, width of the seam narrowed. Granular β-Sialon uniformly scattered in theseam. Effect of holding time on bonding strength has a down trend. Fracture surface ofthe joint shows that the majority of bonding joints began to fracture in the seam,acrossed the seam, end in the ceramic near to the Si₃N₄ceramic/solder interface. Thejoint fractured in the seam when the temperature was low. According to the study ofstrength, at high temperature strength of joint inclued Y rare earth has a down trend.Strength of joint included Nd rare earth was141MPa at1000℃.Interface of joint and microstructure of welding seam was analysed by the TEM.With increasing the temperature, the RE-Si-Al-O phase was formed. Then α-Si₃N₄dissloved in solder. With increasing the N content, the RE-Si-Al-O-N phase was formed.With increasing temperature, β-Si₃N₄dissloved in welding seam. Then the β-Sialonprecipitated. In connected process, the glass phase diffused among silicon nitrideceramic and solder.