In this work, the high-temperature physical and chemical properties of the mixture of zirconium and graphite and of titanium silicides are described. These materials were used for the suppression of grid emission in tubes of high efficiency with thoriated-tungsten cathodes. The evaluation of the properties of these materials was carried out in simple laboratory diodes in vacuum by applying individual components and their mixtures in the form of powder to the electrodes and measuring the emission. The molybdenum cathode was coated with the substance under investigation and heated in steps of 30–50°C from the lowest to the highest temperature. The temperature was controlled by an optical micropyrometer. After every increase in temperature, the emission was observed always for 2 min. The spontaneous increases and decreases of emission apparent on the curves and their relative position permitted the selection of suitable components. By this method the properties of Zr, C, Zr + C, Ti, Si, Ti 5Si 3, TiSi, and TiSi 2 were studied. The results of laboratory tests were verified on an industrial scale. The technology of the production of these anti-emission coatings is described in detail. This method of evaluation could be applied in other technical fields to the study of reactions at very high temperatures, or for the evaluation of high-temperature-resistant materials.