Raman, EPR and ethanol sensing properties of oxygen-Vacancies SrTiO3-δ compounds

Polycrystalline SrTiO3-δ powders with cubic perovskite phase were prepared by solid-state reaction method followed by the creation of oxygen vacancies δ-thermal activated. The Raman spectroscopic investigation was carried out in a frequency range of 100-2000 cm−1, and the second-order Raman modes were observed at room temperature. The Electron Paramagnetic Resonance (EPR) results revealed that SrTiO3-δ samples had evident EPR signals that increased significantly with oxygen-vacancy concentrations. The incorporation of oxygen vacancies was found to decrease the thermal resistivity. Besides, the electrical sensing measurements showed that sensors based on SrTiO2.925 (STO1) and SrTiO2.875 (STO2) exhibited semiconductor behavior, while SrTiO2.75-based sensor (STO3) revealed the introduction of a metallic behavior at low temperature. Furthermore, these measurements confirmed that the resistivity increased after the introduction of the ethanol gas, which indicates that our samples can be considered as sensors for ethanol gas detection. The formation of oxygen vacancies under ethanol exposure at the surface of SrTiO3-δ sensors was evaluated by photoluminescence.