Intrinsically Formed Trivalent Titanium Ions in Sol–Gel Titania

Electron paramagnetic resonance (EPR) room-temperature observation of trivalent titanium in sol–gel titania has been reported. This unprecedented detection of stable paramagnetic signals in this titania, which was treated at 200°–800°C, occurred regardless of whether the atmosphere was reducing, inert, or oxidating. The possibility that the paramagnetic signals may originate from an metal impurity other than titanium was completely excluded by analyzing the samples using three different ion-beam-analysis techniques: Rutherford backscattering spectroscopy, particle-induced X-ray emission resonance, and energy-recoil detection analysis. The paramagnetic signals appeared at precisely the temperature range of the sample dehydroxylation, which suggests a mechanism for explaining these Ti³⁺ EPR spectra.