A new doped silver tin oxide with improved electrical behaviour

Several grades of silver 10-wt.% tin oxide with tellurium oxide additions have been prepared by a powder metallurgy process involving powder mixing, compression, sintering, and second compression to maximum density. The contact parts have been submitted to different electrical tests. After 20000 openings of a 100-A circuit, the erosion loss of 1% tellurium oxide doped silver tin oxide is 13.2 mg compared with 50 mg for internally oxidized silver cadmium oxide. Another test with AC 3 conditions at 100 A of current at opening and 600 A at closing shows that 1% to 1.5% tellurium oxide doped silver/tin oxide has a low temperature rise and very low welding forces compared with nondoped silver tin oxide. 2.0 and 3.0% tellurium oxide shows the same behavior in a 1050-A making current test. The erosion rate is not increased with tellurium oxide additions. The low welding forces result in an improved making capacity in contactor applications