an example of sucg a system is AIN, which is important as a substrate material for electronic packing applications because of its high thermal conductivity. its ability to remove heat from a mounted device is decreased if oxide is present in the GBs. It is made commercially by sintering AIN powder and Y2O3 at temperatures above 1800c. The y2o3 reacts at high temperatures with the oxide coating on the AIN grains to form a liquid phase. On cooling ,the liquid phase crystallizes to form Y-Aloxides (particularly YAG). these phase are located mainly at triple point