Silver-Metal Oxides as Contact Materials

After a short historical survey, the requirements for silvermetal oxide are explained. These requirements are compared with the technical contact properties of the materials, which are discussed for a large number of the most different silver-metal oxides with regard to · welding on make, · erosion on make, · temperature rise of closed contacts after a large number of switching operations, · erosion on break, · arc movement in the magnetic field, · arc extinction. The effect of a third component, dosing materials in low concentrations, is also included. This is followed by a description of the most important methods of manufacture. Starting from internal oxidation on the one hand and sintering on the other, as well as methods which are based on both technologies, the stages of production are represented in diagrammatic form. The results of a large number of experimental investigations lead to the ranges of application of silver-metal oxides and their limits compared with other materials. Looking to the future, it is shown that Ag/CdO will probably be replaced, if the development continues, by the essentially more environmentally acceptable material Ag/SnO2during the next 5-10 years.