Using secondary ion mass spectrometry, an investigation was made of the concentration versus depth profiles of Nb which had been thermally diffused into (100)-oriented yttria-stabilized zirconia single-crystal substrates. The surface morphology of the Nb films and the substrates was analyzed by using atomic force microscopy. The structural disorder and the interface configuration of the samples were investigated by means of X-ray reflectometry. Two types of substrate were used: as-received and reduced. The reduced substrates were obtained by annealing as-received substrates in air for 2h at 1250C. The bulk diffusion coefficient, at 780 to 1000C, for Nb in as-received single crystals, was described by:

D (cm2/s) = 2.93 x 101 exp[-3.91(eV)/kT]

The data for Nb in the reduced substrates were slightly different. It was concluded that the incorporation of Nb into the lattice was governed by the vacancy mechanism.

Diffusion Behaviour of Nb in Yttria-Stabilized Zirconia Single Crystals - SIMS, AFM and X-Ray Reflectometry Investigations. G.Kuri, M.Gupta, R.Schelldorfer, D.Gavillet: Applied Surface Science, 2006, 253[3], 1071-80