Abstract
Diffusion coefficients of activators that are usually used in nickel sleeve of oxide cathode, and activation energies of diffusion are obtained. The diffusion coefficients are deduced by evaluations based on the decreasing characteristics of the activators in thin nickel filaments (50 microns in thickness) heated at a constant temperature between 1173°K and 1573°K for hundred hours. The activation energy is also deduced for each activator from the slope of curve log D_??_1/T.
The experiments are carried out on Mg, Mn, Si, Al, W, and the activation energies are given respectively as 1.5, 2.1, 2.7, 2.9 and 3.8(eV), and the diffusion coefficients are given at two representative temperatures:
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From these results, the order of diffusion ability of activators is considered as Mg→Mn→Si_??_Al→W. Accordingly, it is desirable that the most appropriate activator be selected for each electronic tube to serve its purpose.
