LAUSR

Abstract The mixture of 5 wt% LaB 6 and mechanically alloyed Si-B-C-N powders was conventionally ball-milled and then compacted by spark plasma sintering at 1250–2000 °C and 50 MPa. Densification, microstructural evolution and mechanical properties of the as-prepared La/Si-B-C-N monoliths were investigated. At 1360 °C, sintering initiates coupled with rapid densification caused by particle rearrangement and plastic deformation. Grain-boundary sliding and atomic diffusion lead to further densification when sintering continues. Only SiC and La-containing BN(C) phases are detected in La/Si-B-C-N monoliths sintered at temperatures higher than 1900 °C. The monoliths sintered at 2000 °C show a high fracture toughness (4.6 MPa m −1/2 ) attributed mainly to lamellar La-containing BN(C) grains.