Analysis of Periodic Schottky Deviations from Iridium Filaments

The periodic deviation from the Schottky effect for thermionic emission has been measured for iridium polycrystalline wire over a temperature range from 1500 to 2000°K. A least-squares computer program was used to fit the experimental data with the periodic $F_2$ term predicted by the Miller-Good theory and deduce a complex reflection coefficient for the surface potential. However, the results also indicate that the amplitude of the experimental deviation increases slightly faster with field than is predicted by theory.