Nd doped Y3Al5O12 (Nd:YAG) single crystals were grown by the double crucible method with an automatic powder supply system to control Nd segregation. Grown Nd:YAG single crystal has uniform Nd concentration with +/- 0.02 at% when 30% of the melt was solidified. The optimization of temperature gradient and seed centering is an important growth condition for the double crucible method to prevent asymmetric growth of the crystals. These crystals contained bubbles and Ir-particles. The mechanism causing these crystal inclusions will be discussed in detail.