Experimental Support of the Magnetron Nickel Oxide Cathode Fabrication Process

Abstract

This work is an experimental justification of the choice of the temperature and time modes designed for the heat treatment of real magnetrons, the end result of which is the initial decomposition of barium carbonate into barium oxide. We experimentally determine the temperatures of polymorphic transitions in barium carbonate and the temperature of the dissociation of barium carbonate in different atmospheres (air, argon, carbon dioxide, and vacuum) for the physical modeling of the processes occurring in pumped magnetrons. The phase composition of a test barium carbonate specimen is determined at room temperature by X-ray phase analysis (XPA) on a diffractometer before and after heating. The effect of the temperature and time of isothermal exposure on the phase composition is experimentally investigated on a high-temperature diffractometer. Using a derivatograph, we analyze the chemical and physicochemical processes that occur in the samples during heating. The enthalpy of polymorphic transitions and the activation energy of dissociation are evaluated. Quantitative data are presented that characterize the kinetics of phase transitions for various heat treatment modes and demonstrate the temperature ranges of the existence of different phases. It is shown that reducing the heating rate and increasing the time of heating interruptions slow down the transition of BaCO₃ into BaO. It is established that the powder is sintered when heating barium carbonate.