Research Of The High Sensitive Gas Sensors Based On NASICON

In recent years, more and more harmful gases diffusion from the factory, automobile exhaustor and interior decoration. With the acceleration of industrialization and the improvement of living standard, These gases is serious harm to the human health. Therefor, it is extraordinary significant to research the sensors for detecting and controlling these harmful gases. In this paper, two kinds of gas sensors in allusion to these harmful gases are developed.In this paper the effects of materials preparation method, selection of sensing materials and dopants the doping ratio, the operating temperature and the structure changing on the sensing characteristics have been researchedFirst, we prepared NAISCON by two ways, which were sol-gel process and solid reaction process. Although experimental results show that NASICON prepared by sol-gel process is purer then the material fabricated by solid reaction process, the NASICON prepared by solid reaction process is more easily press into a disc, which is necessary to fabricate an amperometric sensor. Considering these factors, we fabricated the amperometric sensor with NASICON prepared by solid reaction process and produce the mix potential sensor with the NASICON manufactured by sol-gel process.Second, ionic conduction layer has been fabricated with NASICON prepared by solid reaction process for a solid electrolyte amperometric NO2 sensor. The counter electrodes fabricated with carbonates+NaNO2 respectively. The testing results show that:(1) The measurement range for the sensor to NO2 is 10-100 ppb.(2) the sensor with 9 wt.%SrCO3 as the adulterant exhibited excellent selectivity to low concentration NO2.(3) The sensor with 9 wt.%SrCO3 as the adulterant is showed highest sensitivity At 200 oC, the sensitivity of the sensor to 10 ppb NO2 is 40 nA and variation of AI for the sensor is 3.7×103 nA.(4) The sensing mechanism of amperometric NO2 sensor can be explained by the synthesis and decomposition reactions of NaNO2 at the sensing and counter electrodes.Third, The present paper reported an electrochemical Cl2 sensor device based on NASICON and oxide electrodes sensing electrode. Eight kinds of metal oxides (Cr2O3, CuO, ZnO, WO3, NiO, SnO2, Fe2O3, Co3O4) for the sensing electrodes were prepared by chemical precipitation or thermal decomposition processes.(1) Among the oxides tested, Cr2O3 was found to be best suited for the sensing electrode.(2) The device attached with Cr2O3 electrode showed excellent sensing characteristics to 5-50 ppm Cl2 in air at 300℃. The 90%response and 90%recovery times to 10 ppm Cl2 at 300℃for the CrO3-attached device were 5 s and 10 s, respectively.(3) The EMF value of the device was almost linear with the logarithm of Cl2 concentration.(4)It was also observed that the device exhibited excellent selectivity to Cl2 against the other interference gases, such as CO, NO, NO2, H2, C7H8, C2H4 and CH4.(5) The buried reference electrode can effectively improve the sensitivity of the sensor. Based on the excellent sensing properties, this kind of sensor has important application value for detecting chlorine in the atmosphere.