Abstract: An indirectly heated cathode that can enhance the withstand voltage and the efficiency of radiating heat from a heater to a tubular sleeve, and a cathode ray tube using such a cathode. The indirectly heated cathode comprises a hot cathode emitting electrons at one end, and a tubular sleeve including a high melting point metal and having a heater inside. A thermal absorption layer is formed on the inside face of the tubular sleeve and the thermal absorption layer contains a boron compound.

Abstract: A cathode for an electron tube formed by coating the base of the cathode for the electron tube with an alkaline-earth metal carbonate containing at least barium as the alkaline-earth metal, and thermally decomposing in a vacuum to generate an emitter mainly comprising an alkaline-earth metal oxide, wherein a mixture of two or more kinds of alkaline-earth metal carbonate crystalline particles having different shapes is used as the above mentioned alkaline-earth metal carbonate. Since the present invention can provide a cathode for electron tube having improved both cut-off drift and emission characteristic at the same time, it is useful as a cathode for the electron gun of a CRT, or a cathode for the electron gun of an electron microscope.