Planar potentiometric SO₂ gas sensor for high temperatures using NASICON electrolyte combined with V₂O₅/WO₃/TiO₂ + Au or Pt electrode

Abstract

For high temperature application, a planar SO₂ sensor using NASICON as an electrolyte and V₂O₅/WO₃/TiO₂ + Au or Pt as a sensing electrode was fabricated and investigated. In the case of Pt electrodes, the sensor showed the strange response in temperature range from 300–600°C. In the case of Au electrodes, the sensor showed a strange behavior at 300 and 400°C, while at 600°C the sensor showed good response to SO₂. The highest sensitivity with 80–83 mV/decade in the SO₂ range from 20 to 200 ppm was observed at 600°C, although offset shifting was observed in repeated measurements. The sensors showed the potential for good selectivity at 600°C in the case of Au electrodes. The fact that the electric potential difference of the sensor is strongly affected by the electrode materials may intend that the mechanism of the sensor is a mixed potential type.