Ceramic pellets of rutile, with embedded Pt wire electrodes, were heat treated in a manner that changed the normal electrical properties of rutile at room temperature from those of an insulator to those of a semiconductor with rectifying characteristics. This change in electrical properties was accompanied by the development of unusual microstructures in the rutile grains which were analyzed by a combination of techniques including transmission electron microscopy and scanning transmission electron microscopy. These analyses indicated that, under the applied conditions of heat treatment, Pt diffused into the rutile and reacted initially with the TiO2 at oxygen vacancy sites to form point‐defect agglomerates and that these point defects blocked the normal formation of crystallographic shear planes. As the process proceeded by continued Pt diffusion, thin planar precipitates of PtTi3 were formed in epitaxial relation to the surrounding rutile matrix.

Unusual Microstructures in TiO2 Ceramic Pellets with Asymmetrical Electrical Conductivity. Shinozaki, S.S., Donlon, W.T., Meitzler, A.H.: Journal of Applied Physics, 1982, 53[11], 7290-8