Self-diffusion studies were carried out on a two-phase ceramic compound with the nominal composition of (Ti0.3W0.5Cr0.2)B2. At 1000 to 1400C, the diffusivities were determined using secondary ion mass spectrometry and co-implanted and simultaneously diffusing stable 49Ti and 54Cr isotopes. This minimized systematic errors, reduced experimental time and permitted direct comparison of the results. The two-phase nature of the material was directly reflected by non-uniform Cr depth profiles while, for Ti, uniform depth profiles indicated almost the same diffusivities in both phases. The diffusivities of both elements obeyed:

Cr:      D(m2/s) = 6 x 10-8exp[-3.3(eV)/kT]

Ti:      D(m2/s) = 1 x 10-9exp[-3.1(eV)/kT]

These data hinted that no simple vacancy mechanism was operating in the material. The experimental results also suggested that the growth of precipitates at 1600C was controlled by the volume diffusion of Cr and Ti.

Materials Transport in (Ti0.3W0.5Cr0.2)B2 Ceramics: Simultaneous Diffusion of Ion Implanted 49Ti and 54Cr. H.Schmidt, G.Borchardt, C.Schmalzried, R.Telle, H.Baumann, S.Weber, H.Scherrer: Journal of the European Ceramic Society, 2003, 23[6], 991-5