High pressure-high temperature sintering and characterization of ternary boride Cr2AlB2 ceramics

High-purity and well crystalline Cr 2 AlB 2 ceramics were fabricated from Cr and AlB 2 powders using a high pressure and high temperature (HPHT) method. The effects of sintering temperature, duration and pressure on the sintering process were systematically investigated using X-ray diffractometry. Optimal sintering conditions were identified as 1600 °C, 5 GPa, and 1 h. Scanning electron microscopy analysis revealed that the Cr 2 AlB 2 sample possesses an elongated and lamellar microstructure, with individual layers measuring a few hundred nanometers in thickness. Cr 2 AlB 2 samples exhibited a Vickers hardness of 9.9 GPa, with outstanding mechanical properties, including high fracture toughness and Young's modulus of 5.3 MPa m 1/2 and 379.1–434.5 GPa, respectively. Transmission electron microscopy analysis detected edge dislocations, wrinkle defects, lattice twist and distortion within the crystals, all contributing to the enhanced hardness and toughness. X-ray photoelectron spectroscopy analysis reaffirmed prior findings regarding the anisotropic chemical bonding in Cr 2 AlB 2 , characterized by strong intralayer bonds and weak interlayer interactions. The electron transfer and capture between layers are crucial for stabilizing the Cr-B layer substructure.