A Retarding Potential Method for Measuring Electrical Conductivity of Oxide-Coated Cathodes

Abstract

A retarding potential method is developed for measuring the electrical conductivity of normal oxide cathode coatings. The method is limited by normal current measuring devices and can not be used for coatings which have a conductivity to thermionic emission ratio greater than 2 cm/volt. Advantages of the method are: (1) the conductivity of coatings which are in a normal state for thermionic emission may be measured without the use of probe wires or other devices which might impair the thermionic emission of the sample, and (2) conductivity and thermionic emission measurements may be made simultaneously on the same coating sample. The theory of the method is discussed in detail and experimental results obtained using this method on both BaO and (BaSr)O coatings are given.