Electrical Conductivity of Calcium Oxide at High Electric Fields

Abstract

INTEREST in the study of the electrical properties of the alkaline earth oxides as an aid to understanding the physics of the oxide-coated cathode has led to an extension of work previously carried out on the electrical conductivity of calcium oxide at low electric fields¹. In order to obtain activation energies for the conduction processes², it is necessary to determine the conductance at zero applied field as a function of temperature; but information of some value can be obtained from a study of the conductance of the cathode material at higher electric fields than those commonly employed. Reports of investigations at high fields are much less numerous than those of conventional measurements, but the work of Danforth and Goldwater³ and of Nakai, Inuishi and Tsung-Che⁴ may be referred to. Of interest is the recent investigation by Adams and Jacob⁵ on strontium oxide: the behaviour of its high-field conductance appears to be dissimilar to that of barium oxide, the form of the graph of conductance versus applied voltage depending strongly on the temperature of the oxide. The present work on calcium oxide may be of interest in a general comparison with results from the other alkaline earth oxides.