The adsorption and diffusion properties of scandium atom on the surfaces of tungsten and noble metals

摘要

As for the scandate cathode, the performance of Sc atom, including the adsorbability and diffusivity, plays an important role in the emission property and emission stability of the scandate cathode. W is the most widely used matrix metal in thermionic scandate cathodes, however, the cathode suffers from the recovery of scandium after ion bombardment. Herein, the adsorption properties and diffusion performance of Sc atom on the surfaces of W, Ir, Os, Re and Ru are systematically studied with the density functional theory (DFT). It is found that the adsorbabilities and diffusivities of Sc atom on the surface of W, Ir, Os, Re and Ru are in the order as W (0 1 1) Re(0 0 0 1) Ru(0 0 0 1) Os(0 0 0 1) Ir(11 (2) over bar1) and Ir(11 (2) over bar1) W(0 1 1) similar to Os(0 0 0 1) Ru (0 0 01) Re(0 0 01), respectively. The adsorbabilities and the diffusivities of Sc atom on the surface of Re and Ru are higher than those on the surface of W, which suggests that Re and Ru are the potential materials to be the matrices or the coatings of scandate cathodes to improve the ion bombarding insensitivity and electron emission recovery of the cathode.