The conductivity of oxide cathodes. Part 12: Influence of strontium ion migration on matrix conductivity

The donor element in the oxide matrix is now regarded as strontium metal, and in the present Part its movement in an electric field is considered. It is shown experimentally that the donor is positively ionized, can be chemically isolated by solution in a platinum cathode core, is mobile in an electric field at temperatures above 550° K, and is incapable of diffusion in a concentration gradient below 800° K. Excessive concentration of the positive ion is shown to give rise to a dramatic increase in matrix resistivity. It is finally concluded that there exists an optimum donor concentration at which the conductivity of the matrix is at a maximum.