Numerical Analysis Of Thermal Stress For Planar Amperometric Oxygen Sensor With Dense Diffusion Layer And Research On Mechanical Property Of YSZ

The planar amperometric oxygen sensor with dense diffusion layer is a new type ofoxygen sensor. Since it has fast response, high sensitivity, wide scope of measuring oxygen, Itis widely applied. The solid electrolyte layer, one part of the sensor, is sensitive material,which is very important for sensor. The fundamental research of planar amperometric oxygensensor was studied. The main content is as follow:(1) The yttria-stabilized zirconia (YSZ)solid electrolyte ceramic was produced with drypressing molding method and pressureless sintering process. The proper molding andsintering process was designed. Molding process: molding pressure of10Mpa, dwell time of1min；Sintering process by two step sintering process: first of all, up to1500℃, and thencooled to1450℃, holding4h, the temperature-rise rate of5℃/min.(2) The effect on the mechanical properties of YSZ ceramics within different dosage ofyttrium oxide was studied. It was found that,3YSZ ceramic has a good mechanical property,with the relative density of96.7%, an bending strength of285.711MPa；8YSZ ceramic isworst，its mechanical property is far less than3YSZ ceramic’s，with relative density of90.8%,and the bending strength of89.189MPa.(3) The effect on the mechanical properties of8SZ ceramics within different dosage ofnano-Al2O3was studied. it was concluded that,8YSZ ceramic within4wt%nano-Al2O3hasthe best mechanical property, the relative density of94.0%, an bending strength of113.86MPa；8YSZ ceramic within too much nano-Al2O3, its mechanical property can be quicklyreduced instead.(4) A model of the planar amperometric oxygen sensor with dense diffusion layer wasbuilt. The thermal stress coupled field for cold start of the oxygen sensors with densediffusion layer is simulated and analyzed. Loading step voltage instead of constant voltage isa good method to resolve this contradiction of response time and stable working temperature.The result of electro-thermal coupling analysis shows that, response time of this sensor is5s, stable working temperature is800℃. The result of thermo-mechanical coupling analysisshows that, the thermal stress mainly depends on the assembly stress in actual installation. Asthe thermal expansion coefficient of LSCM/3YSZ diffusion barrier material is close to YSZelectrolyte material’s, the LSCM/3YSZ material is used to make oxygen sensor, the maximumthermal stress is less than the rupture strength of all layers, which can overcome the thermalmismatch of LSM and YSZ.