Aluminum nitride (AlN) is a highly interesting material due to its thermal and electrical properties. These properties make it very attractive for electrical applications and components for semiconductors.

In order to fully densify aluminum nitride, many sintering technics are used such as hot-pressing (HP), spark plasma sintering (SPS), and gas pressure sintering (GPS). This latter is a promising method that allows the application of gas, such as nitrogen or argon, at pressure from a few bars to tens of bars. Nevertheless, the use of an additive is crucial for the densification rate and the desired properties. Both parameters are important for the improvement of final properties.

In our work, cerium oxide (CeO₂) is used as an additive during the sintering of aluminum nitride. Preliminary studies showed the formation of cerium aluminates (i.e. CeAlO₃ and CeAl₁₁O₁₈) during sintering [1]. These phases appeared to be formed by the reaction of the amorphous aluminum oxide layer around AlN particles and the sintering additive, cerium oxide. Three sintering methods (HP, GPS, and SPS) were used to obtain different samples with different microstructures.

This study aims to investigate the correlation between grain size and secondary phases with the final properties of the samples. The sintering conditions were optimized to obtain samples with similar secondary phases. The grain size was varied using different sintering methods. Spark plasma sintering was used to obtain small and medium average grain size microstructure while gas pressure sintering and hot pressing were used to obtain big grain size microstructure. The products were characterized with XRD, SEM-EDS, and TEM, and the thermal and electrical properties were measured.
 
[1] M. Coëffe-Desvaux, N. Pradeilles, P. Marchet, M. Vandenhende, M. Joinet, et A. Maître, « Comparative Study on Electrical Conductivity of CeO₂-Doped AlN Ceramics Sintered by Hot-Pressing and Spark Plasma Sintering », Materials, vol. 15, no 7, Art. no 7, janv. 2022, doi: 10.3390/ma15072399.