Abstract: Four oxide nanoparticles, such as yttrium oxide, lanthanum oxide, cerium oxide and zirconium oxide were coated on rhenium filaments by an electrophoretic deposition method. The oxide coatings were examined by scanning electron microscopy, and electron emission characteristics of the oxide-coated rhenium were studied to find alternative oxide materials for replacing the hazardous thorium oxide. Among four oxides tested in this work, yttrium oxide and lanthanum oxide coated rhenium showed enhanced electron emission compared with an uncoated rhenium. However, lanthanum oxide coating evaporated too quickly in a vacuum chamber, and hence yttrium oxide was found to be the only alternative material for use in a routine mass spectrometry. An optimum coating thickness of the yttrium oxide and lanthanum oxide was around 20 μm.

Key words: Electrophoretic deposition, Oxide nanoparticles, Scanning electron microscopy (SEM), Electron emission