Ultra-high purity tungsten and its applications

High purity (> 99.999 wt.%, 5N) or ultra-high purity (> 99.9999 wt.%, 6N) tungsten (W) electrodes are vital to the performance and lifetime of high intensity discharge (HID) lamps. On the other hand, alloys based on high purity (> 99.99 wt.% or 99.995 wt.%, 4N or 4N5) W are used as sputtering targets to deposit the films in semiconductor devices. In this study, a highly efficient and cost-saving method for mass producing 6N W powder has been developed. The 5N and 6N W rods and wires for the electrodes of HID lamps have been manufactured by using this powder. In addition, vacuum hot pressing has been employed to prepare 4N5 tungsten–titanium (W–Ti) and 4N tungsten–silicon (W–Si) sputtering targets successfully. The impurities and microstructures of the developed high purity W products have been investigated and are suitable for lighting, semiconductor and photovoltaic applications.