Methods for fabricating refractory metal scandate nanocomposite powders with homogeneous microstructured refractory metal grains and a uniform nanosized dispersion of scandia are provided. The powders prepared by the sol-gel methods have a spherical morphology, a narrow distribution of particle sizes and a very uniform dispersion of nanosized scandia particles joined to the tungsten grains. The powder particle sizes can range from nanometers to micrometers. The powders can be pressed into porous cathode structures that can be impregnated with emissive materials to produce high current density and long life cathodes for high-power terahertz vacuum electron devices. The sol-gel fabrication methods allow control over the materials, particle size, particle composition and pore size and distribution of the cathode structure by manipulation of the process parameters.

The present disclosure discloses a preparation method of pressed Scandia-doped dispenser cathode using microwave sintering. Embodiments of the present disclosure include dissolving some nitrates and ammonium metatungstate with deionized water to prepare a homogeneous solution. Precursor powder with uniform size is obtained by spray drying, the precursor powder is decomposed, and two-step reduction may be proceeded to form doped tungsten powder with uniform element distribution. The cathode is prepared by one-time microwave sintering. One-time forming of cathode sintering is realized, and sintering shrinkage and sintering time are reduced significantly. The method has excellent repeatability, and the cathode has a homogeneous structure and excellent emission performance at 950° C.

The present disclosure discloses a preparation method of pressed Scandia-doped dispenser cathode using microwave sintering. Embodiments of the present disclosure include dissolving some nitrates and ammonium metatungstate with deionized water to prepare a homogeneous solution. Precursor powder with uniform size is obtained by spray drying, the precursor powder is decomposed, and two-step reduction may be proceeded to form doped tungsten powder with uniform element distribution. The cathode is prepared by one-time microwave sintering. One-time forming of cathode sintering is realized, and sintering shrinkage and sintering time are reduced significantly. The method has excellent repeatability, and the cathode has a homogeneous structure and excellent emission performance at 950° C.

A method to reduce the work function of a carbon-coated lanthanum hexaboride (LaB6) cathode wherein the exposed tip of the cathode is exposed to moisture between two heat treatments is provided. The work function may be reduced by 0.01 eV or more.

A cathode head can include: a first electron emitter filament having a first size; a first grid pair defining walls of a first filament slot having the first filament therein, each grid member of the first grid pair being electronically coupled to different voltage sources; a second electron emitter filament; and a second grid pair defining walls of a second filament slot having the first electron emitter therein, each grid member of the second grid pair being electronically coupled to different voltage sources. The first grid pair can have a first and second grid members; and the second grid pair can have the second grid member and a third grid member. The first grid member and third grid member are electronically coupled to the same voltage source and the second grid member being electronically coupled to a different voltage source.

An array of carbon nanotube micro-tip structure includes an insulating substrate and a plurality of patterned carbon nanotube film structures. The insulating substrate includes a surface. The surface includes an edge. A plurality of patterned carbon nanotube film structures spaced from each other. Each of the plurality of patterned carbon nanotube film structures is partially arranged on the surface of the insulating substrate. Each of the plurality of patterned carbon nanotube film structures comprises two strip-shaped arms joined together forming a tip portion protruding and suspending from the edge of the surface of the insulating substrate. Each of the two strip-shaped arms comprises a plurality of carbon nanotubes parallel to the surface of the insulating substrate.

An apparatus includes an emitter electrode including a phosphorus doped diamond layer with low work function. The apparatus further includes a collector electrode and a vacuum gap disposed between the emitter and the collector. The collector has a work function of 0.84 eV or less.

An apparatus includes an emitter electrode including a phosphorus doped diamond layer with low work function. The apparatus further includes a collector electrode and a vacuum gap disposed between the emitter and the collector. The collector has a work function of 0.84 eV or less.

Disclosed embodiments include vacuum electronic devices, methods of operating a vacuum electronic device, and methods of fabricating a vacuum electronic device. In a non-limiting embodiment, a vacuum electronics device includes a cathode and an anode. At least one focus grid is disposed between the cathode and the anode, and the at least one focus grid is physically disconnected from the cathode. The at least one acceleration grid is disposed between the cathode and the anode, and the at least one acceleration grid is further disposed adjacent the at least one focus grid. The at least one acceleration grid is physically disconnected from the cathode.

Disclosed embodiments include vacuum electronic devices, methods of operating a vacuum electronic device, and methods of fabricating a vacuum electronic device. In a non-limiting embodiment, a vacuum electronics device includes a cathode and an anode. At least one focus grid is disposed between the cathode and the anode, and the at least one focus grid is physically disconnected from the cathode. The at least one acceleration grid is disposed between the cathode and the anode, and the at least one acceleration grid is further disposed adjacent the at least one focus grid. The at least one acceleration grid is physically disconnected from the cathode.