Comparative Study on Electrical Conductivity of CeO 2 -Doped AlN Ceramics Sintered by Hot-Pressing and Spark Plasma Sintering.

Aluminum nitride (AlN) ceramics were prepared by both Hot-pressing (HP) and Spark-Plasma-Sintering (SPS) using cerium oxide as the sintering aid. The characterization of AlN raw powder denoted the presence of an amorphous layer that led to the formation of aluminum oxide. During the sintering process, CeO 2 introduced as a sintering aid was reduced into Ce 2 O 3 . The latter reacted with aluminum oxide to form a transient liquid phase that promotes sintering by both HP and SPS. A reactional path leading to the formation of secondary phases, such as CeAlO 3 and CeAl 11 O 18 , has been proposed according to the pseudo-binary Al 2 O 3 - Ce 2 O 3 . Ceramics obtained from HP and SPS are presented as similar, except for the secondary-phase distribution. The influences of secondary phase composition and distribution on electrical conductivity were evaluated by leakage current measurements. The mechanism of DC conduction and the global conductivity of ceramics were discussed according to the sintering process and the number of secondary phases.