DENSIFICATION AND THERMAL-CONDUCTIVITY OF AIN DOPED WITH Y2O3, CAO, AND LI2O

Small amounts of Li2O result in sintering in the AlN-Y2O3-CaO and AlN- CaO systems at firing temperatures <1600 degrees C. The effect is ascr ibed to reduction of the liquidus temperature. Furthermore, Li2O is re moved by volatization at temperatures from 1300 degrees to 1600 degree s C, and its content decreases several ppm from the initial 0.3 wt%. L i2O-doped AlN specimens containing Y2O3 and CaO additives are well den sified by firing at 1600 degrees C for 6 h, and their thermal conducti vity is 135 W . m(-1). K-1. The effect of Li2O addition on sintering a nd thermal conductivity also is discussed through thermodynamic consid erations.