Solid-state single-crystal growth of YAG and Nd: YAG by spark plasma sintering

Recent studies have shown that many challenges encountered in conventional single crystal growth methods, including high production costs, can be overcome by using the solid-state single-crystal growth (SSCG) approach, which has been recognized as a simple and cost-effective alternative for obtaining single crystals. In this work, Y3Al5O12 (YAG) and Nd3+-doped YAG (Nd:YAG) single crystals were grown via the SSCG method using spark plasma sintering (SPS). The growth of single crystals was initiated at the surface of (110) YAG single-crystal seeds embedded inside YAG and Nd:YAG powder beds, and this growth continued as the surrounding polycrystalline matrix was converted into a single crystal. The application of external pressure during the SPS process has been found beneficial for reducing the porosity of the grown single crystals. Moreover, high Nd3+ doping levels had a positive effect on the conversion kinetics, with a growth rate of almost 50 µm/h, which increased the driving force for single-crystal growth through the solute drag effect. EDS elemental mapping and line scans confirmed the compositional uniformity of the grown single crystals, while EBSD images verified their crystallization in the (110) direction. The obtained results confirm the strong potential of the SSCG technique coupled with SPS for the growth of undoped and highly doped YAG single crystals with excellent quality.