Two-step thermal diffusional bonding of transparent Nd:YAG ceramics

• Experimental setup for thermal diffusional bonding of Nd:YAG ceramics was developed.
• Transmission of bonded Nd:YAG sample was equivalent to that of the starting ceramics.
• Grain growth and coalescence along the bonding interface was observed.

In this article, we report on the process of thermal diffusional bonding of two transparent Nd-doped yttrium-aluminum garnet (Nd:YAG) ceramic samples into monolithic material. The thermal diffusional bonding was conducted via two steps. In the first step the samples mechanically polished to a flatness of λ/20 were placed into an original experimental setup and were bonded together under uniaxial pressure of 30 MPa at 1440 °C for 2 h. The second step consisted in calcination of bonded ceramics at 1780 °C for 20 h under vacuum. The in-line transmittance and absorption coefficient of monolithic Nd:YAG ceramic sample after two-step thermal diffusional bonding was equivalent to that of the starting ceramics. The optical microscopy images of the contact interface revealed disappearance of the contact layer at the bond due to the grain growth and coalescence.