In situ synthesis, structure, and properties of bulk nanolaminate YAl3C3 ceramic

Polycrystalline YAl3C3 ceramic was fabricated by an in situ hot-pressing process using YH2, Al, and C powders as starting materials. The crystal structure of YAl3C3 was determined by X-ray diffraction and ab initio calculations to be a hexagonal space group P63/mmc. The lattice parameters are a = b = 3.424 Å, c = 17.291 Å, and the atomic positions are Y at 2a (0, 0, 0), Al1 at 2d (1/3, 2/3, 3/4), Al2 at 4f (1/3, 2/3, 0.138), C1 at 2c (1/3, 2/3, 1/4), and C2 at 4f (1/3, 2/3, 0.6045). The reaction synthesis path for YAl3C3 was presented. Microstructure observations revealed that YAl3C3 ceramic had plate-like grain morphology. The elastic, mechanical and thermal properties of YAl3C3 were investigated. Most significantly of all, the Young's modulus of YAl3C3 could retain 276 GPa (85% of that at room temperature) at 1500 °C, suggesting that YAl3C3 is a promising lightweight high temperature structural material.