Preparation And Properties Of Limiting Current Type Oxygen Sensor Based On 8YSZ As Solid State Electrolyte

Dense diffusion barrier limiting current oxygen sensor plays an important role in improving the combustion efficiency and decreasing harmful emissions,which is widely used in many fields such as metallurgy,chemical industry,industrial furnace,automobile industry.In this paper,we adopt co-precipitation method to synthesize Y0.08Zr0.92O2-?(8YSZ)solid electrolyte powders and(La0.4Ce0.6O2-?)1-x(FeO1.5)x(x=0,0.04,0.10,and 0.20)mixed ionic and electronic conductor(MIEC)powders.We adopt citric-nitrate method to synthesize La0.7Sr0.3Mn03(LSM)MIEC.The Crystalline structure,microstructure,electronic conductivity,ionic conductivity and total conductivities of 8YSZ solid electrolyte and LSM,(La0.4Ce0.6O2-?)1-x(FeO1.5)x MIEC were characterized by X-ray diffraction(XRD),scanning electron microscopy(SEM),Hebb-Wagner method,AC impedance method,and DC van der Pauw method,respectively.The oxygen sensor with(La0.4Ce0.6O2-?)0.96(FeO1.5)0.04 and 8YSZ was fabricated by Pt sintered-paste method,and the output performance of oxygen sensor was discussed.The oxygen sensor with(La0.4Ce0.6O2-?)0.96(FeO1.5)0.04 and 8YSZ was manufactured by co-pressed and co-sintered method,and the output performance of oxygen sensor was discussed.The oxygen sensor with 8YSZ as substrate,LSM as coating layer was prepared,and the effect of spin coating cycle times,the contain of ethyl cellulose and sintering condition by spin coating on morphology of dense diffusion barrier was investigated,and the output performance of oxygen sensor was discussed.The results are as follows:(1)XRD patterns of the(La0.4Ce0.6O2-?)1-x(FeO1.5)x(x=0,0.04,0.10,and 0.20)powders belong to faced-centered cubic phase.Additional phase such as LaFeO3 appears when x=0.10 and 0.20,indicating that the solid solubility limit of FeO1.5 in La0.4Ce0.6O2-? ranges from 4 mol%to 10 mol%.The density,electronic,and ionic conductivity first increases and then decreases with increasing FeO1.5 dopant.La0.4Ce0.6O2-?)0.96(FeO1.5)0.04 has the highest conductivity.(2)The limiting current oxygen sensor fabricated by Pt sintered-paste method shows good performance.The detecting oxygen range,operation temperature and operation voltage are 0.7%-12.9%,850?,and 1.55V-1.74V,respectively.Limiting current is proportional to oxygen concentration,and the linear equation is IL(mA)=9.43+1.19 xo2(0.7 mol%<xo2<13.2 mol%).The value of limiting current increases with the temperature rise,and the relationship between logarithm limiting current and temperature was linear dependence:logIL(mA)=5.37-4666.81/T(K-1).The polarization resistance declines with increasing oxygen concentration from 80.5 ? to 44.7 ? at 850? under oxygen concentration of 0.7%-13.2%.(3)The dense diffusion barrier limiting current oxygen sensor fabricated by co-pressed and co-sintered method shows good performance.The measured oxygen concentration is 0.3%-11.2%at 850?.The limiting current is proportional to oxygen concentration:IL(mA)=10.60+1.35xo2(0.3 mol%<xo2<11.2 mol%).The value of limiting current increases with the temperature rise,and the relationship between logarithm the limiting current and the reciprocal of temperature is linear dependence:log IL(mA)=3.26-2085.12/T(K-1).(4)The limiting current oxygen sensor based on LSM dense diffusion barrier and 8YSZ solid electrolyte is developed by slurry spin coating method,which exhibits good sensing performance.The optimized parameters are as follows:the content of ethyl cellulose is 3 wt%,the coating cycle number is 7,and the sintering condition is 1400? for 10 h.The limiting current oxygen sensor has wide range of oxygen detection and the detection range of oxygen increases with the increase of temperature:0.4%-9.9%at 700?,0.2%-13.8%at 750?,0.5%-15.1%at 800?,and 0.7%-20.8%at 850?.The oxygen sensor exhibits good limiting current plateau,and the value of limiting current depended linearly on the oxygen concentration:IL(mA)=13.25+4.23 xo2(0.4 mol%<xo2<9.9 mol%)at 700?,IL(mA)=10.41+6.75xo2(0.2 mol%<xo2<13.8 mol%)at 750?,IL(mA)=25.40+11.03xo2(0.5 mol%<xo2<15.1 mol%)at 800?,and IL(mA)=21.02+17.47 xo2(0.7 mol%<xo2<20.8 mol%)at 850?.The oxygen sensor developed by spin coating method has best performance and sensitivity at 850?.The relationship between logarithm the limiting current and the reciprocal of temperature is:log IL(mA)=6.29-4712.60/T(K-1).Therefore,slurry spin coating method is promising in fabricating oxygen sensor.