Structure Design And Process Research Of The Novel Planar Potentiometric Automobile Oxygen Sensor

According to Nernst principle, the traditional planer potentiometric automobile oxygensensor must have air chamber layer in the structure so as to provide invariable oxygen partialpressure. The structure of the air chamber layer is complicated, high cost, difficult to befurther miniaturized, at the same time, the cavity structure will greatly reduce overall strengthof the sensor. A novel planar potentiometric automobile oxygen sensor employingcerium-based oxygen storage material as the solid oxygen partial pressure reference layer toreplace air chamber layer is proposed in this paper, in order to simplify the fabrication processof the traditional planar potentiometric automobile oxygen sensor, reduce manufacturing costsand improve the performance of the sensor, which provides the theoretical and technicalfoundation for planar oxygen sensor and miniaturization. The main research contents are asfollows:(1) Focus on the core components of the novel planar automobile oxygensensor-YSZ(yttria stabilized zirconia) solid electrolyte molding and sintering processes werestudied. The8YSZ dual powders were dry pressed and pressureless sintered. The moldingprocess parameters including the molding pressure, pressure holding time and dosage ofbinder were optimized. The sintering scheme based on orthogonal test was designed. Theinfluence of the sintering process parameters including sintering temperature, heating rate,holding time, sintering method on the sintering properties and mechanical properties of8YSZwas discussed and their optimization value were obtained. The results show that the greenceramic with the relative density of54.9%was pressed by adopting the optimizedmolding process parameters with the dosage of PVA of10%wt, the forming pressure of10Mpa, the pressure holding time of30s and the8YSZ ceramic with the relative density of98.3%and the bending strength of100.3Mpa was prepared by adopting the optimizedsintering process parameters with the sintering temperature of1500℃, holding time of4h,heating rate of5℃/min, sintering methods of naked burning.(2) Employing the cerium oxide-based solid-state storage material as the solid-statereference, the overall structure of the novel planer potentiometric oxygen sensor was designed,and a preliminary study of its production processes and test systems was carried.(3) The thermal stress coupled field for cold start of the planar automotive oxygen sensorwas simulated in this paper. By the method of loading a step voltage instead of constantvoltage, the response time can be reduced greatly. The result of the electrothermal coupled analysis shows that the active area of the sensor has reached work temperature above300℃at t=3s. Each layer appears the maximum temperature gradient at t=5s. The result of thethermomechanical coupled analysis shows that equivalent stress of each layer is graduallyincreasing and reaches maximum at t=20s in the cold start. The assembly stress generated bythe assembly boundary condition is the main contribution of equivalent stress. The finiteelement analysis results showed that the designed sensor can meet the requirements ofresponse time and strength. It was believed that the modeling techniques and computationalapproaches incorporated in this study were useful and can be applied for the development ofsimilar products.