Design, fabrication and performance of SO2 sensor based on LaF3 solid-electrolyte

LaF₃ is attractive because of its possible application at room temperature, in addition to other advantages and it has been investigated for measuring various types of gases. A solid-state gas sensor with the structure of (working electrode) SO₂,Pt/LaF₃/Sn,SnF₂ (reference electrode) was developed for detecting sulfur dioxide at room temperature. With numerical simulation, a series of working electrodes with different line widths were designed. Typical lift-off process was applied to produce the micro pattern of Pt working electrode layer on one side of the solid electrolyte (LaF₃) wafer. The sensor cell was electrolysed in order to form SnF₂ layer with about 3nm thickness at the interface between the Sn film and the LaF₃ wafer. The EMF of the sensor was found to vary logarithmically with a change in sulfur dioxide partial pressure, following Nernst´s equation. Experiments show the working electrode with different line width somewhat influences on performance of the gas sensor. The sensing mechanism of the sulfur dioxide sensor was also investigated.