Densification of low-density boron carbide by Li doping and its microstructural characterization

Lithium (Li)-doped boron carbide (B 4 C) has generated widespread attention for its potential to enhance mechanical properties. Nevertheless, the influence of the Li solid solution on the microstructure and mechanical properties of B 4 C ceramics remain unclear. In this research, the microstructure of Li-doped B 4 C was investigated in meticulous detail. Through X-ray diffraction, X-ray photoelectron spectroscopy, and Raman spectroscopy analysis, it was confirmed that Li successfully solubilized in B 4 C at 1 500°C under 50 MPa for an 8 min, resulting in lattice expansion. Further insights from electron energy loss spectroscopy revealed the integration of Li into the crystal lattice and alterations in the C–B–C chains. Furthermore, the Li 2 O content significantly affected the densification and microstructure of B 4 C. Relative density increased from 91.2% (B 4 C) to 99.2% (9 wt.% Li 2 O–B 4 C), accompanied by a transition from a few intragranular planar defects to high-density twins. Mechanical property tests demonstrated that 9 wt.% Li 2 O–B 4 C exhibited optimal comprehensive mechanical performance, with a flexural strength of 533 ± 27 MPa, fracture toughness of 3.71 ± 0.29 MPa∙m 1/2 , hardness of 33.3 ± 0.6 GPa, and a density of just 2.45 g/cm 3 , surpassing that of pure B 4 C.