- Title
- Synthesis and thermionic properties of tungsten-barium titanate composites
- Creator
- Hasan, Muhammad M.; Sugo, Heber; Kisi, Erich
- Relation
- Materials Science and Engineering B: Advanced Functional Solid-state Materials Vol. 194, p. 14-20
- Publisher Link
- http://dx.doi.org/10.1016/j.mseb.2014.12.020
- Publisher
- Elsevier
- Resource Type
- journal article
- Date
- 2015
- Description
- The potential of novel tungsten-barium titanate composites as thermionic emitters is explored. Composites ranging from 20% to 80% tungsten by mass were prepared by sintering in an Ar-H2 atmosphere. XRD and SEM studies indicate four major micro-constituents; W, BaTiO₃, Ba₄(Ti,Fe)₁₂O₂₇ and BaWO₄. Richardson work functions (φR) and Richardson constants (ΑR) were determined using a Schottky diode arrangement at temperatures ranging from 1223 to 1473 K. Work functions ranged from 2.67 eV to 3.32 eV with a shallow minimum at 40% by mass W and were relatively constant (~2.7-2.8 eV) in the range 30-70% by mass W. The decrease in work function was accompanied by a strong decrease in AR from 39.3 A cm⁻² K⁻² to 0.02 A cm⁻² K⁻² over the range 20-70% by mass W. The reduction in both φR and AR was associated with the major conversion of the surface to BaWO₄ and Ba₄Ti₁₂O₂₇ during the activation treatment before emission testing.
- Subject
- thermionic emission; barium titanate; tungsten; work function; Richardson constant
- Identifier
- http://hdl.handle.net/1959.13/1319865
- Identifier
- uon:23991
- Identifier
- ISSN:0921-5107
- Language
- eng
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