Synthesis of Nanocrystalline Electron Emissive Materials with Homogenous Composition in Nanoscale

Abstract

Abstract-In this research, specific stoichiometric mixture of nanocrystalline barium carbonate, calcium carbonate, and aluminum oxide was fabricated by using the sol-gel combustion method. This mixture is used as emissive materials on impregnated cathodes which make up high power vacuum microwave tubes such as klystrons. Composition uniformity and particle size of emissive materials affect the electron emission properties of impregnated cathodes. In this study, dry gel and heat treated powder at 500 °C are investigated by thermal analysis (TG/DTA), X-ray diffraction (XRD), scanning electron microscopy (SEM), and energy dispersive X-ray spectroscopy (EDX). The results show that dry gel combusts at 260 °C , and that during combustion transforms from an amorphous phase to a nanocrystalline phase. The average crystallite size of the powders which is calculated by Debye-Scherrer's method based on the XRD patterns is under 45 nm. The results of SEM and EDX of powder after heat treatment at 500 °C show that the particle size of powder is under 100 nm, and the chemical composition of emissive material is uniform at nanoscale.Index Terms-Dispenser cathode, emissive material, nanopowder, sol-gel combustion synthesis.

Study the Effect of Nanoemissive Materials on M-Type Cathode Performance

“…1) An emissive material mixture with the molar ratio of 5:3:2 was prepared by sol-gel combustion technique as discussed in our previous work [10]. The nano emissive material powder fabrication process sequence is illustrated in Fig Afterwards, the stabilized nitrate-citrate sol was heated at 100 °C to obtain a porous dry gel.…”

Effect of CaO on Phase Composition and Properties of Aluminates for Barium Tungsten Cathode

“…The most widely used electronic emission materials in Ba-W cathodes are aluminates. According to the different molar ratios of BaO, CaO and Al 2 O 3 in aluminates, they can be categorized as 612 (i.e., n BaO :n CaO :n Al2O3 = 6:1:2) [ 6 , 7 ], 411 [ 8 ], 532 [ 9 ], and 311 [ 10 ] aluminates.…”