The effects of various technological processes on the electronic structure of vanadium-doped TiO2 crystals were studied. The EPR spectra give clear evidence that by suitable thermal treatment in a reducing atmosphere the tetravalent vanadium ions could be transferred from the substitutional to the interstitial positions. The four inequivalent spectra corresponding to the four interstitial octahedra were analyzed and interpreted in terms of a microscopic model. The measured values of the components of the g-tensor and hyperfine interaction tensor were: gx = 1.9865, |A x| =45.4 x 10-4/cm; g y = 1.9930, |Ay| = 60.5 x 10-4/cm; gz = 1.9407, |Az| = 111.4 x 10-4/cm. The line-width was found to be approximately 2.8G. The intensity of the absorption lines was one-tenth of the intensity of the original resonance of the substitutional V4+. The deviation of the axes of the magnetic coordinate systems of the four non-equivalent ions with respect to the substitutional sites was found to be φ = ±10°(±0.5°).

Paramagnetic Resonance of Interstitial V4+ in TiO2. Kubec, F., Šroubek, Z.: The Journal of Chemical Physics, 1972, 57[4], 1660-3