Методами электронной спектроскопии для химического анализа, спектроскопии характеристических потерь энергии электронов и оптической спектроскопии исследована электронная структура кристаллитов оксида бария, который определяет эмиссионные свойства как металлопористых, так и скандатных катодов. Установлено, что другие элементы (кальций, алюминий, скандий, вольфрам), входящие в состав катодных материалов, растворяются в оксиде бария, существенно влияя на его электронную структуру и соответ-ственно на эмиссионные свойства. Результаты исследований позволили сформулировать представления о физическом и физико-химическом механизмах влиянии скандия на снижение работы выхода скандатных катодов по сравнению с катодами других типов.
High-resolution X-ray diffraction method (XRD) is used to determine sizes and crystallographic orientation of the nanocrystallites of the Pd and Pd_5Ba phases in palladium–barium cathode. Electron spectroscopy for chemical analysis (ESCA) is used to study Ba and Pd chemical states in cathode material and determine the phase composition including dissolved microimpurities in the phases. The comparison of the XRD and ESCA data makes it possible to reveal effects related to the formation of the BaO crystallites in the cathode material, which are responsible for the emission properties. Electron-energy loss spectroscopy is used to determine the concentration of oxygen vacancies in the BaO crystallites that are formed in the cathode material due to activation. An original crystallite model of the working palladium–barium cathodes that is based on the results of this work may serve as an alternative to the known film model and makes it possible to optimize technology of cathode fabrication and activation.
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