Effect of Spark Plasma Sintering Conditions on the In-situ Synthesis
of Polycrystalline CeB6 Ceramics
Erhan Ayasa, Levent Köroğlua
a
Anadolu University, Engineering Faculty, Department of Materials Science & Engineering,
Eskişehir – TURKEY
*erayas@anadolu.edu.tr
Keywords: CeB6, Cathode Material, Spark Plasma Sintering, In-situ Synthesis, Polycrytalline
Abstract
Rare-earth hexaborides, REB6, have attracted much attention because of their unique characteristics
including high melting point, chemical stability, efficiency, superconductivity, magnetic properties,
and thermionic emission. The advantages of using REB6 derive from their crystal structure, which is
composed of RE metal atoms are surrounded by a boron octahedron network. In REB6 group, cerium
hexaborides (CeB6) are the most promising cathode materials due to having Kondo compound
behaviour and lower work function (2.5 eV), lower operation temperature, higher resistance to C
contamination and lower volatility than lanthanum hexaborides (LaB6) which means a longer service
life.
Compared to the nanowires, thin films and singlecrystallines, the polycrystalline bulk materials can
provide large size, low cost, simple preparation and can be fabricated easily to various devices.
Therefore, there are great research prospects for bulk polycrystalline CeB 6 cathode materials especially
for its excellent field emission or thermionic emission properties. Spark Plasma Sintering (SPS) is the
most favorable method for effective bulk CeB6 fabrication which is fundamentally different from CVD,
E-Beam Floating Zone Melting and Hot-Pressing Sintering methods. It obviously contributes to full
densification, reduces the sintering temperature, shortens the sintering time and improves the
mechanics and emission properties by Joule heat and spark plasma generated by high pulsed electric
current.
In current study, synthesis and densification of CeB 6 from starting powders of cerium oxide (CeO2) and
amorphous boron (B) by SPS (FAST) was investigated. Dense CeB6 samples were obtained by
applying a two-step heating schedule under specific SPS conditions. Phase and microstructural features
of the samples were investigated extensively. It was the first time to obtain high dense bulk
polycrystalline CeB6 effectively from CeO2 and amorphous B with two-step SPS regime.