Investigations of V₂O₅-based LPG sensors

Abstract

Sensor characteristics of V₂O₅ dispersed on oxide supports such as Al₂O₃, TiO₂ and ZrO₂ with respect to various gases and vapours including liquefied petroleum gas (LPG) have been investigated. Of all the systems studied, 20 mol% V₂O₅ dispersed on ZrO₂ shows the highest sensitivity for LPG, the log sensitivity-log concentration (in ppm) plots being linear up to 1000 ppm or more. The sensitivity is not affected by humidity or recycling. Addition of P₂O₅ to V₂O₅ however destroys the sensitivity. Considering all aspects, 20 mol% V₂O₅/ZrO₂ is suggested for use as a practical LPG sensor. ESR spectroscopy indicates the formation of V⁴⁺ species on exposure of V₂O₅/ZrO₂ or TiO₂ to LPG. In-situ high-temperature X-ray diffraction measurements show the formation of an unusual monoclinic form of VO₂ on exposure to LPG at 625 K which gets oxidized back to V₂O₅ on exposure to air.