Sintering behavior of direct nitrided AlN powder

Classified direct nitrided (DN) aluminum nitride (AlN) powders were examine d by dilatometry to study the effect of particle size on sinterability. The shrinkage behavior of three DN powders was compared to that of a commercia l, carbothermally produced, AlN powder. Yttrium oxide was added to AlN powd er as a sintering aid. Two distinct features of the resulting shrinkage cur ves, corresponded to particle rearrangement coincident with yttrium alumina te formation and high temperature sintering. The presence of coarse particl es in the original DN powder, greater than 8 mum, distinguished it from the other powders studied and appeared to have the greatest influence on the s intering behavior. For fine powders without coarse particles (> 8 mum), the synthesis method did not seem to affect the shrinkage. The grain size dist ribution of the sintered parts mirrored the particle size distribution of t he four powders studied. Thermal conductivity (TC) of the sintered AIN bodi es was strongly dependent on the oxygen content of the starting powders. (C ) 2000 Elsevier Science B.V. All rights reserved.