Preparation And Study Of SO₂ Gas Sensor Based Upon Solid Electrolyte

SO2 in air will not only have bad effect on the human environment, even will bring different degree damage to creatures on the earth. To control the emission of SO2, more and more attention has been paid on SO2 detection technology, which has greatly promoted the development of SO2 sensor. Mixed-potential-type SO2 gas sensors based on solid electrolyte, has low production cost, simple equipment structure, and has the advantages of high sensitivity, fast response and other advantages, get numerous researchers favor. In this paper, the author choose two kinds of solid electrolyte materials 8YSZ and NASICON, which are widely applied, prepared 3 kinds of type SO2 gas sensor based on mixed potential type, the performance of each sensor has been studied, and the sensitive mechanism of the sensor has also been discussed from the micro view. This thesis mainly includes the contents below:1. A kind of mixed potential type SO2 gas sensor based on YSZ and Ag-Ag2SO4-BaSO4 electrode was fabricated, and the sensing characteristics of the sensor in the non-equilibrium atmosphere was studied. The device with the Ag2SO4-BaSO4 ball-milled for 20 h showed the highest sensitivity (slope= 46.5 mV/decade, and R=0.997) to the SO2 gas over a range of 20-500 ppm at 600 ℃. And the device with the metallic Ag mixed within the auxiliary phase showed the better sensing performances and has the best sensitivity at the lower temperature (400℃) with the sensitivity 68.7 mV/decade and the fit of linear was 0.99. The test results revealed that the sensor with PtY as reference electrode has better performance and the content of O2 has little effect on the applied of the sensor. All sensors have good repeatability and stability.2. A planar SO2 sensor based on NASICON and Na2SO4-BaSO4 sensing electrode has been fabricated, and the sensing performance of the sensor in the non-equilibrium atmosphere was studied. The research results showed that there was a good linear relationship between the logarithm of SO2gas concentration and sensor output electric potential value, and in low temperature of 260 ℃, the sensor has ideal performance to the test gas, the sensitivity reached up to 160 mV/decade, which is similar to the best results of the literature that were test under equilibrium atmosphere at temperature of 550-600 ℃. In addition, the device has good repeatability and stability.3. The SO2 gas sensor based on NASICON and with NaRe(SO4)2 as the sensing materials has been fabricated, and the sensing properties were explored in the non-equilibrium atmosphere. First, use the method of alcohol-water mixed solvent to prepare sodium lanthanum sulfate with ultrafine particles at room temperature. The test results showed that, at each temperature, there is a good linear relationship between the output EMF of the sensor and the logarithmic of SO2 concentrations, and the sensor had the best sensing properties when the working temperature was 260 ℃ with the ideal sensitivity of 136 mV/decade, proved that our proposed scheme is feasible and has good research value. In addition, the AC impedance was applied to test the sensor in different concentrations SO2 gas.