Niobium diffusion in niobium-doped titanium dioxide

Abstract

The present work studied the self-diffusion coefficient of 93Nb in Nb-doped TiO2 single crystal (4.3 at.% Nb) at high oxygen activity [p(O2) = 21 kPa] over the temperature range 1,073 to 1,573 K. The diffusion-induced 93Nb concentration profile was determined by using secondary ion mass spectrometry (SIMS). The subsequently determined self-diffusion coefficient of 93Nb exhibits the following temperature dependence:\(D_{{}^{93}{\text{Nb}}} = 1.77 \times 10^{ - 9} \,{\text{m}}^2 \,{\text{s}}^{ - 1} \,\exp \left( {\frac{{ - 197 \pm 9\,{\text{kJ}}\,{\text{mol}}^{ - 1} }}{{{\text{RT}}}}} \right)\). This study builds upon a similar study performed previously for 93Nb tracer diffusion in undoped TiO2, and identifies the effect of compositional change on self-diffusion behaviour. The obtained activation energy has been considered in terms of migration and formation enthalpies of titanium vacancies.