The most common use of the substance “barium oxide” is based on its hygroscopic property - the ability to absorb water. That is why directly in the chemical industry it is used as a component for the production of barium peroxide. In industry, oxide is indispensable in the manufacture of ceramic magnets. In addition, in modern conditions, barium oxide, the formula of which is BaO, has found great application in microelectronics and electrical engineering. For the production of magnetoceramics, barium ferrate is used, which is obtained by combining barium and iron oxide powders in a powerful magnetic field under pressure.
However, the main area of application is the production of thermionic cathodes. Even at the beginning of the last century, a German scientist Venelt was studying the law of electron emission, which was recently discovered by the English researcher Richardson. For experiments, Venelt used pieces of platinum wire. The first experimental results fully confirmed the conclusions made subsequently by the English physicist. But then the experiment failed, and Venelt suggested that the electron flux is much higher than the norm because any impurities could appear on the surface of the working substance - platinum. Having verified his assumption, Venelt found that the source of the deviation of the magnitude of the electron flux is barium oxide, which hit the platinum surface as a lubricant in technical devices used in the experiment. The conclusions of Venelt for a long time remained unrecognized, because the scientific community could not experimentally reproduce his experience. It took almost a hundred years for the English physicist Kohler to prove the correctness of Venelt. Kohler, on the basis of repeated experiments, proved that if barium oxide is subjected to gradual heating at low pressure, then the intensity of thermionic emission increases rapidly.
Only in the thirties of the last century, the German chemical scientist Paul suggested that the electrons are activated precisely because of the presence of barium impurities in the oxide. During the reaction, which is carried out at low pressure, part of the oxygen escapes from the oxide. The remaining barium is ionized and thereby contributes to the appearance of free electrons. These electrons were the ones that left the crystalline structure upon heating and which Venelt had once observed.
And only at the beginning of the second half of the last century the validity of this hypothesis was finally proved. Chemists A. Bundel and P. Kovtun (USSR) were able not only to numerically establish the concentration of barium impurities in the oxide, but also experimentally compare its value with the value of the thermal emission flux. That is why barium oxide is used as an active substance in the manufacture of thermionic cathodes. An example is an electron beam, which creates an image on the screen of a simple TV or computer monitor. Here, barium oxide acts as a source of flow.
If you try to dissolve this substance in water, it is found that barium oxide reacts with water when the solution is heated. This gives the substance barium hydroxide - a white powder with a melting point of only 78 ° C. This compound interacts well with carbon dioxide, and therefore an aqueous solution, often called "barite water", is widely used as a reagent for carbon dioxide.
As a starting and necessary component, the compound is a part of various coloring materials, lubricants and oils. Such use of barium oxide was predicted by D.I. Mendeleev.