Preparation And Properties Of Nano-structured Composite For NO_x Sensors

NO_x is not only a major source of environmental pollution, but also harmful to human body, so it is necessary to develop the sensor for NO_x with fast response, high sensitivity and suitability for high temperature operation. Solid electrolyte of NO_x sensors have gradually been concerned by scholars, and among them the lanthanum silicate solid electrolyte with apatite structure has excellent electrical properties. To study the effect of Si-double-doped lanthanum silicate on the electrical properties of the electrolyte, La_0.8Sr_0.2Fe_0.8Cu_0.2O_3-??LSFC?, LaCrO₃?LCO? nano composite sensitive electrodes were prepared by wet chemical impregnation technique. Lanthanum silicate samples and sensitive electrodes were characterized by XRD, SEM and EDX measurements. NO₂ amperometric sensor with lanthanum silicate substrate was assembled and then the electrochemical performance of the sensor was evaluated.Si-double-doped lanthanum silicate La10Si5 Al XNYO₂7±??N= W, In; X=0, 0.5, 0.7, 0.9,1; Y=1, 0.5, 0.3, 0.1, 0? was prepared by high temperature solid phase synthesis method.It was found that the electrical conductivity of lanthanum silicate co-doped by Al and W,In was higher than that doped by single element. The conductivity of LSAW was the highest at 800 °C??=2.23×10-2 S·cm-1?, and conductivity of LSAI was slightly less than the former??=2.12×10-2 S·cm-1?. It was indicated that Al could improve the conductivity of electrolyte by replacing a Si with a small amount of W or In.LSFC nano particles was prepared by wet impregnation technique and used to prepare the NO₂ amperometric sensor. The sensitivity of the sensor was tested, and the sensor demonstrated the highest sensitivity and the largest response at 800 °C. The sensor using LSFC nano particles exhibited good stability and selectivity.LCO nano particles was prepared by wet impregnation technique and NO₂ amperometric sensor was prepared. The linear relationship between the sensor response signal and the NO₂ concentration was good. The sensor had good stability and reproducibility. O₂ had significant influence on the selectivity of the sensor. The sensitivity of the sensor reduced after the Na element was impregnated with LCO.