Mechanical properties of phase-pure bulk Ta₄AlC₃ prepared by spark plasma sintering and subsequent heat treatment

High-purity and bulk Ta₄AlC₃ ceramics were successfully fabricated by spark plasma sintering (SPS) and subsequent heat treatment, using the raw materials including TaC and Ta₂AlC powders. These raw materials were first synthesized by self-propagation high temperature synthesis from elements tantalum, aluminium and carbon black powders, followed by pressure-less sintering. The as-fabricated bulk Ta₄AlC₃ was relatively stable when subjected to heat treatment at elevated temperature of 1500 °C. Moreover, prolonging the heat treatment time resulted in bigger grain sizes and higher densities of the Ta₄AlC₃. The flexural strength and the fracture toughness of the Ta₄AlC₃ fabricated by SPS were found to be 411 MPa and 7.11 MPa·m¹/², respectively. After the heat treatment at 1500 °C for 8 h, the flexural strength and the fracture toughness of the Ta₄AlC₃ could reach 709 MPa and 9.23 MPa·m¹/², respectively. The special structural characteristics of the ternary ceramics and the increase of density after the heat treatment are the main reasons for the variation in mechanical properties of ternary ceramics.