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With the growing problem of automobile exhaust pollution, the study of automotive oxygen sensor is very meaningful, nitrogen oxides accounts for a large proportion of automobile exhaust. AC impedance spectroscopy of the NOx sensor in different temperature(500°C，600°C，700°C) and NO2 of different concentrations （100ppm，500ppm，1000ppm）in this paper, the influence of temperature and gas concentration on NOx sensors is explored.

Currently, Yttria-stabilized zirconia solid state electrolyte are widely used in various fields . The basic performance of Yttria-stabilized zirconia (5YSZ) prepared by different synthesis methods and sintering temperatures are studied in this paper ,their phase compositions and microstructure are studied with XRD and SEM. The ionic conductivity of 5YSZ sintered at different temperature are studied with A.C. impedance spectroscopy measurement.

Through Mechanical grounding method, CaZrO3 – 8YSZ(8% in mol yttria stabilized zirconia) electrolyte samples with different amounts of CaZrO3 at 10wt%, 20wt%, 30wt% were sintered at different temperatures in Muffle furnace. The decomposition temperature of CaZrO3 is 825°C-900°C under one atmosphere. At high temperature, CaZrO3 decomposes into CaO and ZrO2. So Y2O3-CaO-ZrO2 complex is composed. The effects of the sintering temperature and the contents of the CaZrO3 on the conductivity, porosity, flexure strength, hardness were investigated. XRD and SEM were used to analyse the compositions and microcosmic morphology.

Electrode slurry made of Pt powder was brushed on both surfaces of the sintered ZrO2 substrate. And then the Pt electrodes were sintered under various temperatures. The microstructure of the surface of the electrodes was characterized by scanning electronic microscope. The electrochemical properties of the electrodes were investigated by electrochemical impedance spectroscopy (EIS). The results show that the sintered temperature of the electrode has a remarkable effect on the microstructure of the electrode and the Pt electrode show favorable electrochemical catalysis performance.

In some applications such as automotive oxygen sensor, 5mol% Y2O3stabilized zirconia (5YSZ) is generally used because it has both excellent ionic conductivity and mechanical properties. the automotive oxygen sensor would experience a cyclic change from high temperature (engine running) environment to the lowtemperature damp environment (in the tail pipe when vehicle stops). The microstructures change with coupled conditions of thermal cycle and dump environment in the 5mol%Y2O3–ZrO2 (5YSZ) system was examined by XRD，Raman spectroscopy and scanning electron microscopy (SEM) in this paper.