The densification behavior, microstructure, mechanical, and thermionic emission properties of LaB6‐SiC composite

Abstract The LaB ₆ ‐SiC composite with the different SiC content (0, 15, 30, 36, 50, 90, and 100 wt.%,) was densified by spark plasma sintering. The effects of SiC content on the densification behavior, microstructure, mechanical, and thermionic emission properties of LaB ₆ ‐SiC composite were systemically investigated. The results show that all the rapid shrinkage occurred at the heating stage during densification, and LaB ₆ ‐36 wt.%SiC composite owned the maximum shrinkage rate of 1.5 mm/min at T = 1798°C. The highest relative density of the composite decreased from 98.18% to 95.01% as the SiC content increased from 15 wt.% to 90 wt.%, under which the morphology of LaB ₆ grain evaluated from the equiaxed to elongated structure, and LaB ₆ grain size varied in the range of 5.05–11.42 μm. The similar eutectic structures were observed in the LaB ₆ ‐36 wt.% SiC composite because of some LaB ₆ grains melting. Both the highest fracture toughness of 5.15 ± 0.56 MPa.m ^1/2 and the highest bending strength of 313 ± 4.7 MPa belonged to the LaB ₆ ‐36 wt.% SiC composite, which also exhibited thermionic emission current density of 10.74 A/cm ² and work function of 2.99 eV at T = 1873 K.