Niobium diffusion in niobium-doped titanium dioxide.

Abstract

The present work studied the self-diffusion coefficient of Nb-93 in Nb-doped TiO2 single crystal (4.3 at.% Nb) at high oxygen activity [p(O-2) = 21 kPa] over the temperature range 1,073 to 1,573 K. The diffusion-induced Nb-93 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-93Nb - 1.77 x 10(-9) m(2) s(-1) exp(-197 +/- 9 kJ mol(-1)/RT). This study builds upon a similar study performed previously for Nb-93 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. © 2009, Springer.