Densification of hard β‐boron based ceramics by spark plasma sintering at larger heating rate

ABSTRACT The densification process of β‐boron via spark plasma sintering (SPS) with controlled heating rates (50–300°C/min) was investigated at different temperatures from 1000°C to 1800°C. Systematic characterization reveals that enhanced heating rates (300°C/min) effectively suppress the volatilization of B 2 O 3 impurities, promoting in situ formation of boron‐rich oxide (B 6 O) through reactions between boron and B 2 O 3 . The amount of the retained B 6 O phase in the boron matrix increased with heating rates, which effectively accelerate the densification behavior of boron , achieving near‐full density (2.33 g/cm 3 ) with residual porosity < 0.3% in consolidated boron ceramics. Resultant ceramics demonstrate good combination of properties, including high Vickers hardness (31.0 ± 1.8 GPa at 9.8 N) and low thermal conductivity (13.8 W·m −1 ·K −1 at room temperature and 5.8 W·m −1 ·K −1 at 873 K), the latter was governed by intensified phonon–phonon scattering with less contributions from electrons (< 1‰).