MICROSTRUCTURE AND THERMAL-CONDUCTIVITY OF AIN CERAMICS CONTAINING ADDITIVES

The effect on AIN ceramic of the addition of V2O3, Vb(2)O(3), Er2O3 an d CaO were investigated using scanning electron microscopy (SEM), tran smission electron microscopy (TEM) and thermal conductivity measuremen ts. The effect of grain boundary segregation and second phase distribu tion on the thermal conductivity are discussed. The Er2O3-CaO- and the Yb2O3-CaO- AIN ceramics have a higher thermal conductivity than the C aO- and the Y2O3-CaO- AIN ceramics. This is explained on the basis of the free energy of formation (Delta G degrees), the vaporization of th e sintering additives and the microstructural development. Oxidation o f freshly cleaned surfaces of those AIN ceramics was studied.