In-situ synthesis and densification of CeB6 ceramics by spark plasma sintering from CeO2 and B powders: Effect of boron content and boron particle size on microstructural, mechanical and electrical properties

Abstract

In-situ synthesis and densification of polycrystalline bulk CeB6 ceramics were carried out by Spark Plasma Sintering technique using CeO2 and coarse & nano B powders. Two-step heating schedule was applied via optimizing both synthesis and sintering temperatures using FactSage thermochemical software. The influence of boron particle size and content on the physical, microstructural, mechanical and electrical properties of CeB6 ceramics were investigated. The obtained results exhibited that the content of additional phases (B2O3 & B4C) decreased with the decreasing of boron content (from 31.5 to 23.5 wt%). The reduction of boron particle size (from 1 μm to 250 nm) enhanced fracture toughness values of the investigated ceramics. CeB6 ceramic sintered using nano boron in 8 wt% lack ratio possessed highest CeB6 content (98.4 vol%), high hardness (16.0 ± 2.0 GPa), high fracture toughness (2.8 ± 0.5 MPa m1/2) and low electrical resistivity (1.58x10−1 Ω m). Hence, polycrystalline bulk CeB6 ceramics, sintered at 1950 °C for 15 min under 15 kN by SPS from CeO2 - coarse B powder mixture in 8 wt % lack B ratio, have a usage potential as electron emitters especially in electron microscopes.