EFFECTS OF TRANSITION-METAL ADDITIONS ON THE PROPERTIES OF ALN

Transition-metal oxide additions to AlN ceramics produced no significa nt deterioration in thermal conductivity. In the present study, TiN, Z rN, TaC, NbC, W, and unidentified Hf phases, found as fine particles l ocated inter- and intra-granularly, were distributed randomly in the A lN. Phases containing Fe, Co, and Cr, on the contrary, always were loc ated at the three grain points. Most of the added transition-metal com pounds turned the ceramics black or gray. The shading mechanism was at tributed to optical absorption by the surfaces of the electrically con ductive fine particles and to multiple reflections among these particl es.