Consolidation and high-temperature strength of monolithic lanthanum hexaboride

In this study we explored the densification, microstructure evolution, and high-temperature properties of bulk lanthanum hexaboride. LaB6 bulks were consolidated using spark-plasma sintering only in the temperature range between 1400 degrees C and 1700 degrees C. We adopted flash spark plasma sintering (SPS) of LaB6 using a direct current heating without a graphite die. We observed a peculiar grain-size gradient when coarse grains exceeding 300 mu m were observed on the top side of the specimen, while the bottom side had a grain size of 15-20 mu m. Such large grain was not observed using SPS at 2000 degrees C, suggesting that these might originate from a local overheating. Based on the three-point flexural tests, it was observed that the toughness and strength of the LaB6 were acceptable at room-temperature (3.1 +/- 0.2 MPa m(1/2), 300 +/- 20 MPa). However, at 1600 degrees C, these parameters would decrease to 1.3 +/- 0.1 MPa m(1/2) and 120 +/- 40 MPa, respectively.

Automated summary

This study investigated the densification, microstructure evolution, and high-temperature properties of bulk lanthanum hexaboride (LaB6). Spark-plasma sintering was used to consolidate LaB6, and it was observed that the toughness and strength decreased at high temperatures.