Transport and hardness properties of Cr₂TiAlC₂ MAX phase synthesized by reactive spark plasma sintering

Cr₂TiAlC₂ MAX phase was synthesized for the first time by reactive spark plasma sintering (SPS) from pure metallic precursors. A systematic study of each SPS parameter was performed to promote the formation of the pure phase. The transport properties of the resulting pellet were probed and compared to a conventionally synthesized sample made from pure Cr₂TiAlC₂ densified powder. The electrical conductivity was measured to be 8.31 × 10⁵ S.m^-1 at 298 K, while the thermal conductivity was measured to be 11.76 W.m^-1.K^-1 at 298 K, one of the lowest values reported for a MAX phase. The measured Vickers hardness was 7.62 ± 0.16 GPa at a load of 19.8 N, which is about 40% higher than samples synthesized by hot pressing, making it the hardest 312 MAX phase reported to date. Although Cr₂TiAlC₂ was confirmed to be a poor thermoelectric compound, exhibiting a low Seebeck coefficient of -4.2 μV.K^-1 at 298 K. These results provide a baseline for comparing structural and transport properties prior to etching into MXenes, thereby helping to better understand the influence of dimensional reduction on thermoelectric performance. Overall, these results demonstrate that reactive SPS is a rapid and efficient method for MAX phase synthesis.