Densification and Properties of La1-xCexB6-Al2O3 Ceramics Prepared by Spark Plasma Sintering

A simple and effective method is proposed for producing polycrystalline La 1- x Ce x B 6 (LaB 6 , La 0.75 Ce 0.25 B 6 , La 0.5 Ce 0.5 B 6 , La 0.25 Ce 0.75 B 6 , and CeB 6 )-Al 2 O 3 ceramics. La 1- x Ce x B 6 solid-solution powders were first prepared by the reaction between lanthanum oxides, cerium oxides, boron carbide, and aluminum powders at 1573 K, during which a trace amount of Al 2 O 3 (1–3 wt.%) was inevitably introduced. Subsequently, highly dense (> 98.5%) La 1- x Ce x B 6 -Al 2 O 3 ceramics were produced using spark plasma sintering (SPS) technology at 1850°C, and the results revealed that the existence of Al 2 O 3 can enhance the mechanical properties of La 1- x Ce x B 6 by pinning the grain boundaries and refining the grains. Among the samples, the La 0.5 Ce 0.5 B 6 -Al 2 O 3 composition exhibited the most excellent mechanical properties, which were 22.8 GPa, 4.14 MPa m 1/2 , and 271 MPa for the Vickers hardness, fracture toughness, and flexural strength, respectively. Moreover, compared to the polycrystalline LaB 6 and CeB 6 bulks, the work functions of La 1- x Ce x B 6 bulks were lower, and the presence of Al 2 O 3 had a slight influence on the work function of La 1- x Ce x B 6 .