Transparent YAG ceramic/sapphire composite fabricated by pressureless direct thermal diffusion bonding

Transparent YAG ceramic/c-plane sapphire composites were successfully fabricated by pressureless direct thermal diffusion bonding at 1650 ℃ for 10 h in a vacuum. The bonding interfaces could be well defined between YAG ceramic and sapphire, and effective diffusion lengths from YAG to sapphire were calculated to be about 0.5 μm for Nd, Yb and Y ions by Fick’s second diffusion law. Around the bonding interface, neither crystallization of YAG ceramic nor ceramization of sapphire were observed, and besides, growth of YAG grains as well as variation of sapphire growth striation under heating probably induced the instability or even crack of the composite. In addition, precisely parallel polished contact surfaces of ceramic and sapphire are required for enhancing bonding strength. This work presented a clear vision for the bonding interfaces of YAG ceramic/sapphire composite, and will pave the way for robust and efficient composite laser media.