抄録
To raise the capacity of W contacts, it is important to unify the size of grains by doping. The author has this more quantitatively according to under various conditions of contacts and found the following facts. In the case of heavy loads, high purity and a coarse interlocking structure is required but in the case of light loads, the purity may be lower and the grain size finer. Still more strictly speaking, the grade of grain size and purity must be decided appropriately according to the magnitude of the electr ical and mechanical loads. Of course in this case uniform grain size is required. In the case of heavy loads, W contacts made from tungstic oxide containing a large quantity of Al2O3 such as 0.4% irrespective of the existence of the second or third less volatile additive oxides may be used with advantage, while in the case of light loads those which contain 0.4 per cent of SiO2, 0.2 per cent of Na2O and 0.2 per cent of K2O are suitable.
