Warming-Up of the Cesium Film on the Tungsten Coating of Niobium-Zirconium Alloy Oxidized at 550-1300 °C

Despite the fact that the film of Nb₂W₂O itself is optimal for cesium, the presence of carbon and W₂C, which cannot be removed, in the material of the specimen and CO and COCs they form with oxigen and oxigen and cesium, respectively, causes the formation of other nonoptimal compounds with cesium: NbCOCs - at the lower level of the relief and W₂COCs - at the upper one. These compounds have almost the same heat resistance as the optimal film of sub-bronze NbW₂OCs at the lower level. As a result, φ_min with Cs becomes by 1.6 eV higher than that for pure monocrystalline W, Nb, and Mo-Nb alloy. What this means is the thermion collector (TIC) from this material can operate maximum 50 percent of its capacity in spite of stability of basic properties of the films with Cs in wide temperature ranges of oxidation and warming-up. Hence it is necessary to take measures for decreasing the amount of carbon in the material which the TIC is made from in order to improve its efficiency. (author)