Understanding the surface structure evolution and electron emission behaviors during the activation of Ir-coated dispenser cathodes

被引:7
作者
Chen, Xiaoyang [1 ]
Liu, Hexiong [1 ]
Cai, Yongfeng [1 ]
Zhou, Wenyuan [1 ]
Chen, Shuqun [1 ]
Peng, Jian [2 ]
Yang, Yunfei [1 ]
Wang, Jinshu [1 ]
机构
[1] Beijing Univ Technol, Fac Mat & Mfg, Key Lab Adv Funct Mat, Minist Educ, Beijing 100124, Peoples R China
[2] Wuhan Univ Technol, State Key Lab Adv Technol Mat Synth & Proc, Wuhan 430070, Peoples R China
基金
中国国家自然科学基金;
关键词
Dispenser cathodes; Iridium film; Phase transition; Thermal electron emission; WORK FUNCTION; IRIDIUM COATINGS; THERMO-CALC; ENERGY; 1ST-PRINCIPLES; PERFORMANCE; DENSITY; MODEL; OXIDE; OS;
D O I
10.1016/j.vacuum.2022.111016
中图分类号
T [工业技术];
学科分类号
08 ;
摘要
Metal coated dispenser cathode is of great interest due to its low operation temperature, high current density and long lifetime, however, the emission mechanism is still far from being fully understood. In this work, the tungsten dispenser cathodes were coated with iridium film of 300 nm in thickness. The phase transition and surface structure evolution during cathode activation was systematically investigated. The as-deposited iridium coating shows a columnar grain morphology with ultrafine size. Upon heating for 1 h at 1150 degrees C, a multiple-layer of Ir/ Ir3W/IrW was detected and it fully converted to IrW layer after 4 h heat treatment. Such a structure evolution can be well explained based on thermodynamics. The Ir -> Ir3W -> IrW phase transition induces obvious film thickening and grain coarsening. The full activation could increase the emission current density from 17.35 A/cm(2) to 30.92 A/cm(2) at 1050 degrees C. Density function theory (DFT) simulation results demonstrate the enhanced emission of IrW-coated cathode may be due to its balanced adsorption behaviors with Ba and O atoms. Our findings will provide deeper insights into the design and development of metal coated cathodes with better performance.
引用
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页数:9
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