Simultaneous diffusion of a radio-isotope by two different modes: sulfur-35 in nickel oxide crystals

Anomalous diffusion behavior may occur when the same diffusing species can occupy two different lattice sites in the base compound. In an ionic crystal, the same diffusing species may occupy two different lattice sites and become positively or negatively ionized. When the reaction rate is negligibly small between these two oppositely charged diffusing ions, the diffusion proceeds by a double mode independent diffusion mechanism. An application is given to sulfur tracer diffusion in nickel oxide. The ionization status of sulfur in nickel oxide is also discussed. (author)