Abstract: The electron emission portion of a cathode for an electron gun has layers of substrate material formed from a ceramic powder such as Aluminum nitride. The substrate layers have conductive traces formed on them, the conductive traces made from sintered tungsten or alternatively a refractory foil. When current is passed through the conductive traces, heat is coupled to a cathode which is thermally coupled to the heater assembly. In another embodiment of the invention, one of the layers of the heater includes a thermionic emission material and optionally a work function lowering material such as BaO, which allows the outer layer of the multi-layer heater to directly emit electrons. In another embodiment of the invention, a control grid is formed on a layer above the thermionic cathode layer, which provides for a complete electron gun assembly having a heater, cathode with a reduced work function material, and control grid to be fabricated as a single unit at the same time.