High Temperature XPS/AES Investigation of Mo-La2O3 Cathodes Ⅱ. Variation of Lanthanum During Activation Processes
来源期刊：JOURNAL OF RARE EARTHS2000年第2期
论文作者：WANG Yi-man WANG Jin-shu ZUO Tie-yong NIE Zuo-ren ZHOU Mei-ling ZHANG Jiu-xing
Key words：rare earths; molybdenum; lanthanum oxides; cathode; XPS/AES; electron emission;
Abstract: The changes of the valence state of lanthanum in the Mo-La2O3 model cathode specimens were systematically studied by in-situ XPS/AES analyses from room temperature to 1550 ℃. The experimental results show that the valence of lanthanum changes during the activation processes. As the temperature increases, the lattice oxygen in La2O3 is dissociated, resulting in partial reduction of the lanthanum to LaOx(x<3/2). In addition, the lanthanum-rich phase diffuses from bulk into the surface of the sample. The lack of lattice oxygen in this phase has a favorable effect on emission, which leads to a lower work function for the Mo-La2O3 cathode.
WANG Yi-man1，WANG Jin-shu1，ZUO Tie-yong1，NIE Zuo-ren1，ZHOU Mei-ling1，ZHANG Jiu-xing1
(1.School of Materials Science and Engineering, Beijing Polytechnic University, Beijing 100022, China)
Abstract:The changes of the valence state of lanthanum in the Mo-La2O3 model cathode specimens were systematically studied by in-situ XPS/AES analyses from room temperature to 1550 ℃. The experimental results show that the valence of lanthanum changes during the activation processes. As the temperature increases, the lattice oxygen in La2O3 is dissociated, resulting in partial reduction of the lanthanum to LaOx(x<3/2). In addition, the lanthanum-rich phase diffuses from bulk into the surface of the sample. The lack of lattice oxygen in this phase has a favorable effect on emission, which leads to a lower work function for the Mo-La2O3 cathode.
Key words:rare earths; molybdenum; lanthanum oxides; cathode; XPS/AES; electron emission;
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