CHARACTERIZATION OF THE MICROSTRUCTURE OF SINTERED ALN BY SEM AND TEM

A series of AlN samples with Y2O3, Yb2O3, Er2O3, CaO as sintering aids were characterized using scanning electron microscopy (SEM) and trans mission electron microscopy (TEM), with the objective of understanding the effects of grain size, grain boundary segregation and second-phas e distribution on density and thermal conductivity. The higher thermal conductivity of Er2O3-CaO and Yb2O3-CaO doped materials, in compariso n with CaO and Y2O3-CaO doped samples, is rationalized in terms of the ease of evaporation of the sintering aids and the microstructure. Oxi dation behavior of fresh ion-milled surfaces of AIN samples was also s tudied.