- Title
- Single-step low-temperature synthesis routes for (Ba, Ce, Gd) hexaborides and their thermionic emission properties
- Creator
- Hasan, Muhammad M.; Kisi, Erich; Sugo, Heber
- Relation
- Journal of Alloys and Compounds Vol. 916, no. 165474
- Publisher Link
- http://dx.doi.org/10.1016/j.jallcom.2022.165474
- Publisher
- Elsevier
- Resource Type
- journal article
- Date
- 2022
- Description
- Rare-earth/alkaline-earth hexaborides with high chemical stability and low work function have recently attracted much interest as promising thermionic cathodes. Their synthesis at low temperatures without post-synthesis purification treatments is still a significant challenge. The present work demonstrates a simple synthesis technique to produce pure barium, cerium and gadolinium hexaborides (BaB6, CeB6, and GdB6). For each hexaboride, a batch of samples was created by first milling highly pure precursor powders and then firing at various temperatures in a low-vacuum furnace. The synthesised products were characterised using X-ray diffraction (XRD), scanning electron microscopy (SEM), and electron dispersive spectroscopy (EDS). Their thermionic properties were investigated utilising a Schottky device. Pure BaB6, CeB6, and GdB6 were successfully synthesised at lower temperatures (≤1400 °C). Nanocrystalline CeB6 was found to be produced at the lowest temperature of 1200 °C. The mean particle size of pure CeB6 and GdB6 synthesised is seen to be in the sub-micron range, with the exception of large BaB6 particles. The estimated work functions of the BaB6, CeB6, and GdB6 cathodes are 1.61 ± 0.18 eV, 2.50 ± 0.09 eV, and 2.42 ± 0.09 eV, respectively. These findings imply that hexaborides, as promising thermionic emitters, can be easily produced at low temperatures.
- Subject
- rare-earth hexaborides; borothermic reduction; structural properties; electron emission; Schottky device
- Identifier
- http://hdl.handle.net/1959.13/1488805
- Identifier
- uon:52541
- Identifier
- ISSN:0925-8388
- Language
- eng
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