Bulk diffusion of niobium in single-crystal titanium dioxide.

The present work reports the tracer diffusion coefficient for (93)Nb in rutile TiO(2) single crystals using secondary ion mass spectrometry (SIMS). The determined tracer diffusion coefficient exhibited the following temperature dependence in air ( p(O2) = 21 kPa) over the range 1073-1573 K: D93(Nb) = (4.7 m2 s(-1))x10(-7+/-0.4) exp ((-244 +/- 9 kJ mol-1)/RT) Through comparison to the self-diffusion of (44)Ti in rutile TiO(2), (93)Nb is interpreted to diffuse via the interstitialcy mechanism. The obtained tracer diffusion data are useful for ensuring compositional control during the processing of Nb-doped TiO(2)-based semiconductors using solid-state reactions between Nb(2)O(5) and TiO(2).