Development of silver zinc oxide for general-purpose relays

The switching behavior of silver cadmium oxide (Ag/CdO), silver tin oxide (Ag/SnO/sub 2/) and silver iron oxide (Ag/Fe/sub 2/O/sub 3/) contact materials is compared to silver zinc oxide (Ag/ZnO) materials having different amounts of additives. Endurance tests were performed in a commercial general-purpose relay, subjected to resistive, inductive and inrush current loads. Results showed the performance of Ag/ZnO to be significantly dependent on the amount of additives and their grain size. The optimum Ag/ZnO was found to be equivalent or superior to other silver metal oxides depending on the applied load. Thus a substitution of Ag/CdO by an environmentally harmless Ag/ZnO material is possible.