On the reduction of NS-doped tungsten blue oxide—Part II: Mechanistic considerations

Abstract

Part I of this paper gave a review of the literature. A detailed description of experimental observations on the influence of the NS-dopants (K, Al, Si) on the hydrogen reduction of tungsten blue oxide is given in Part II. Alterations in the suboxide sequence as compared to undoped oxides, intermediate formation of β-W, and W separation from dopant–T-O compounds (bronzes, tungstates) during the transition WO 2→W were observed. Incorporation of the dopants, as necessary for the development of non-sag properties in the final wire, occurs via CVT overgrowth of dopant phases in the WO 2→3W step. Particle size of those phases increases with increasing reduction temperature.