A potentiometric SO₂ gas sensor based on the Li₃PO₄-Li₂SiO₃ solid electrolyte thin film

A potentiometric sulfur dioxide (SO₂) gas sensor based on the Li₃PO₄-Li₂SiO₃ solid electrolyte thin film was developed. The sensor was based on a galvanic cell O₂, SO₂, Au, Li₂SO₄-V₂O₅|Li₃PO₄-Li₂SiO₃|Au, SO₂, O₂. The Li₃PO₄-Li₂SiO₃ thin film was deposited on the Al₂O₃ substrate by RF magnetron sputtering, and the Au patterns were fabricated as the electrodes. The sensing electrode materials of Li₂SO₄-V₂O₅ with different dopants TiO₂ and MgO were prepared, and as the ratio of Li₂SO₄:TiO₂ is 1:1 (mol) with 5 wt. % V₂O₅ and 5 wt. % MgO, the sensor showed relatively good response characteristics to SO₂ at 450 °C. Then, the sensor was further tested at the working temperature from 400 °C to 500 °C. The results show that the sensor has good response to SO₂ at 400-450 °C, and the sensitivity is 90.15-57.19 mV/dec. The response and recovery times are 20-40 s and 2.5-4 min, respectively, when the gas concentration of SO₂ increases from 10 ppm to 100 ppm and then decreases to 10 ppm. At 425 °C, the sensitivity is close to the theoretical values, and the final recovery potential of the sensor is almost consistent with the initial potential.