Patent ID: 7138754

Claim:
An oxide cathode for an electron tube, the oxide cathode comprising: a sleeve for a heater; a metal substrate formed on the top of said sleeve; and an electron emission material layer coated on said metal substrate, said electron emission material layer having a density of 1.1 to 1.7 g/cm 3 , the electron emission material layer formed by coating a carbonate paste composition comprising: an alkaline earth metal carbonate, an organic blowing agent being thermally decomposable to generate gas, and a vehicle, on the metal substrate by screen printing and thermally treating the coated carbonate paste, with said electron emission material layer further comprising a needle-shaped conductive material, with said alkaline earth metal carbonate being contained in an amount of 30–60% by weight, and said needle-shaped conductive material being contained in an amount of 3–15% by weight based on the total weight of said carbonate paste composition of said electron emission material layer.