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The complex method of quality control of the microwave devices cathode matheriales

DOI 10.18127/j15604128-201805-04


V.I. Kapustin – Dr.Sc.(Phys.-Math.), Professor, Leading Specialist, Technical Center «Basic Technologies of EVD», JSC «Pluton» (Moscow); Professor, Department of Nanoelectronics, RTU MIREA (Moscow)
I.P. Li – Ph.D.(Eng.), Director, Technical Center «Basic Technologies of EVD», JSC «Pluton» (Moscow)
A.V. Shumanov – Deputy Director, Technical Center «Basic Technologies of EVD», JSC «Pluton» (Moscow)
S.O. Moskalenko – Bachelor, Process Engineer of the 1st category, Technical Center «Basic Technologies of EVD», JSC «Pluton» (Moscow)

The cathode materials of microwave devices are metal oxide compositions, differing in the composition of the metal and oxide phases and manufacturing technology. The interaction of the metallic and oxide phases proceeds along their boundaries, which determines the nature of the emission inhomogeneity and the structure of the emission-active centers on the cathode surface. This article is devoted to the development of a complex method for monitoring the quality of cathode materials, which allows to determine the shape, average size and thickness of the thermionic emission centers on the surface of cathodes, the average distance between the centers of thermionic emission, the degree of activation of the thermal emission centers, the relative area of the emission-active surface of the cathodes, and the effective and true work function cathode materials.
A complex technique has been developed that allows for accurate measurement of the current-voltage characteristics of cathode ma-terials, that is, recording them in steps of 0.1…0.2 V with subsequent analysis of their nature, determining the parameters of the in-homogeneity of the cathode material - the temperature dependences of the average size of the thermoemission centers on the cathode surface, centers of thermoemission, the relative area of the emission-active surface of cathodes. Taking into account the inhomogeneity parameters of cathode materials, it is possible to determine the true values of the work function of the emission-active centers on the cathode surface, as well as their temperature dependences, which gives information on the degree and nature of the activation of the barium oxide crystallites, which are emission-active centers on the cathode surface.
It is shown that in order to obtain reliable results, the analysis of current-voltage characteristics should be carried out from zero values of the cathode-anode voltage in the direction of its increase, which is necessary for correct extraction of rectilinear sections of current-voltage characteristics in the region of current limitation by space charge and in the region of the Schottky effect. It is established that the analysis of the current-voltage characteristics of the cathode material in the region of deviation from the Schottky law makes it possible to determine the average thickness of barium oxide crystallites that determine the thermionic properties of cathode materials and also calculate the diffusion coefficient of oxygen vacancies in barium oxide crystallites. It is shown that the analysis of the dynamics of the change in the temperature coefficient of the work function in the temperature range 650−750 K makes it possible to estimate the concentration of oxygen vacancies in the barium oxide crystallites, that is, to determine the degree of activation of the cathode material.

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