Chemical bonding theory of single crystal growth and its application to ϕ 3′′ YAG bulk crystal
The growth of YAG bulk crystals was studied using both theoretical calculations based on the anisotropic chemical bonding conditions and practical growth via the Czochralski (Cz) method. The chemical bonding theory of single crystal growth quantitatively describes the anisotropic bonding behaviors of constituent atoms during crystallizing, which can be applied to the thermodynamic growth of YAG single crystals. Both bonding conditions and crystal symmetry determine the projection configuration along the pulling direction and crystal ridges in the crystal shoulder of YAG grown along  direction. During Cz growth process of YAG single crystals, the relative low growth rate along <110> directions results in the exposure of surfaces normal to <110> directions. However, the chemical bonding energy density at the intersection of two adjacent <110> growth directions is higher, leading to the exposure of surfaces normal to <112> directions and the truncated-hexagon configuration of YAG along  direction. ϕ 3′′ YAG single crystal was successfully grown. Our present work provides a promising approach to achieve controllable growth for functional bulk crystal via both thermodynamic and kinetic controls.