Cathode assembly, electron gun assembly, electron tube, heater, and method of manufacturing cathode assembly and electron gun assembly

A cathode assembly comprising:

• a thermally conductive insulating substrate comprising an anisotropic pyrolytic boron nitride and having a pair of opposing surfaces;
• a cathode base member formed on a first of said pair of opposing surfaces of the insulating substrate;
• a heating member comprising an anisotropic pyrolytic graphite layer and provided on a second of said pair of opposing surfaces of the insulating substrate to heat the cathode base member;
• and
• an electrode terminal joined to the heating member through a conductive layer serving as a joining material, the conductive layer comprising a material selected from the group consisting of nickel, titanium, molybdenum, tungsten, niobium, tantalum and an alloy containing any one of titanium, molybdenum, tungsten, niobium or tantalum.