Effects of Arcing in Air on the Microstructure and Morphology of Silver-Based Contact Materials in Correlation With Their Electron Emission Properties

The effects of arcing on the microstructure and morphology of silver-based contacts were investigated in correlation with their electron emission properties. Silver pastilles were subjected to electrical arcs in air, at atmospheric pressure and room temperature, and after that introduced into the vacuum chamber for the electron work function measurements. We demonstrated that the electromechanical conditioning by successive electrical arcs affects the surface characteristics such as microstructure, roughness, and photoelectron work function. Breaking arcs in air cause a remarkable increase in the electron work function of the silver-based contact material by progressive formation of metal oxides. The observations made by a scanning electron microscope (SEM) and the microanalyses made by an energy dispersive spectrometer (EDS) of the cathode surfaces show the surface composition evolution of these contacts used under industrial conditions, and enabled us to have evidence about the various observed phenomena.