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The effect of samarium doping on structure and enhanced thermionic emission properties of lanthanum hexaboride fabricated by spark plasma sintering
Author(s) -
Zhou Shenlin,
Zhang Jiuxing,
Liu Danmin,
Hu Qianglin,
Huang Qingzhen
Publication year - 2014
Publication title -
physica status solidi (a)
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.532
H-Index - 104
eISSN - 1862-6319
pISSN - 1862-6300
DOI - 10.1002/pssa.201330152
Subject(s) - spark plasma sintering , materials science , thermionic emission , samarium , lanthanum , doping , analytical chemistry (journal) , work function , electrical resistivity and conductivity , sintering , microstructure , optoelectronics , metallurgy , electron , chemistry , metal , inorganic chemistry , electrical engineering , physics , chromatography , quantum mechanics , engineering
Single‐phase polycrystalline solid solutions (La 1− x Sm x )B 6 ( x = 0, 0.2, 0.4, 0.8, 1) are fabricated by spark plasma sintering (SPS). This study demonstrates a systematic investigation of structure–property relationships in Sm‐doped LaB 6 ternary rare‐earth hexaborides. The microstructure, crystallographic orientation, electrical resistivity, and thermionic emission performance of these compounds are investigated. Analysis of the results indicates that samarium (Sm) doping has a noticeable effect on the structure and performance of lanthanum hexaboride (LaB 6 ). The analytical investigation of the electron backscatter diffraction confirms that (La 0.6 Sm 0.4 )B 6 exhibits a clear (001) texture that results in a low work function. Work functions are determined by pulsed thermionic diode measurements at 1500–1873 K. The (La 0.6 Sm 0.4 )B 6 possesses improved thermionic emission properties compared to LaB 6 . The current density of (La 0.6 Sm 0.4 )B 6 is 42.4 A cm −2 at 1873 K, which is 17.5% larger than that of LaB 6 . The values of Φ R for (La 0.6 Sm 0.4 )B 6 and LaB 6 are 1.98 ± 0.03 and 1.67 ± 0.03 eV, respectively. Furthermore, the Sm substitution of lanthanum (La) effectively increases the electrical resistivity. These results reveal that Sm doping lead to significantly enhanced thermionic emission properties of LaB 6 . The compound (La 0.6 Sm 0.4 )B 6 appears most promising as a future emitter material.