Niobium segregation in TiO_2

摘要

The present paper reports the effect of oxygen activity p(O_2) on Nb segregation in a polycrystalline specimen of Nb doped TiO_2 (2.91 at.- percent). The determined segregation induced enrichment factor following annealing at 1773 K in p(O_2)=10 Pa and p(O_2)=21 kPa is 3.1 and 7.3 respectively. The data on the effect of p(O_2) on the segregation induced Nb enrichment factor are considered in terms of defect disorder of Nb doped TiO_2 and the related lattice charge neutrality requirements. The reported segregation data may be used for controlled modification of surface concentration gradients in TiO_2 through the imposition of well defined gas phase composition during processing procedures.