Paramagnetic Resonance of Interstitial V4+ in TiO2

The effects of various technological processes on the electronic structure of vanadium-doped TiO2 crystals have been studied. The EPR spectra give clear evidence that by suitable thermal treatment in a reducing atmosphere the tetravalent vanadium ions can be transferred from the substitutional to the interstitial positions. The four inequivalent spectra corresponding to the four interstitial octahedra have been analyzed and interpreted in terms of a microscopical model. The measured values of the components of the g-tensor and hyperfine interaction tensor are: gx = 1.9865 ± 0.0005, | Ax | = 45.4 ± 0.5 × 10−4 cm−1; gy = 1.9930 ± 0.0005, | Ay | = 60.5 ± 0.5 × 10−4 cm−1; gz = 1.9407 ± 0.0005, | Az | = 111.4 ± 0.5 × 10−4 cm−1. The linewidth was found to be approximately 2.8 G. The intensity of the absorption lines is 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 nonequivalent ions with respect to the substitutional sites was found to be φ = ± 10° (± 0.5°).