The conductivity of oxide cathodes. Part 13: Thermal disruption of the matrix

The Joule heating of a matrix, resulting from inelastic collisions of electrons against the hollow-pore walls, is not a uniform phenomenon but tends to concentrate on a relatively small number of particles. These preferred particles are raised in temperature much above the ambient temperature of the matrix and are accordingly subject to an accelerated rate of thermal dissociation. By suitable experimental artifices, the thermal breakdown of these particles is examined, and it is shown that they evolve oxygen gas in negative-ion form and become themselves positively charged by dissolved alkaline-earth-metal ions. Under suitably accelerated conditions, the rate of oxygen generation can become so great that the positively charged particles are blown by a propulsive gas jet from the surface of the matrix into the surrounding vacuum.