Study On CaZrO₃based Dense Diffusion Barrier Limiting Current Oxygen Sensor

Dense diffusion barrier limiting current oxygen sensor can accurately measure the oxygen concentration in the air.In industrial production,accurately consuming the detected oxygen concentration cam reduce exhaust emissions and improve energy efficiency.In this thesis,8YSZ was prepared by the co-precipitation method with Zr OCl₂·8H₂O and Y（NO₃）₃·6H₂O as raw materials.The Y_0.1Ca_0.9Zr_1-xCo_xO_3-δand Ca Zr_1-xNi_xO_3-δmixed conductors were prepared by the solid-state reaction method with Zr O₂,Ca CO₃,Co₃O₄,Y₂O₃and Ni O as raw materials.The Ca Zr_1-xNi_xO_3-δmixed conductor was prepared by the molten salt method.By characterizing its phase composition,micro-structure,electronic conductivity and total conductivity,a suitable mixed conductor is selected as the dense diffusion barrier for the oxygen sensor.The oxygen sensor was prepared by the Pt sintered-paste method and its sensing performance was studied.At the same time,the relationship between its limiting current and oxygen concentration was explored.The conclusions are as follows:1.The main crystal phase of 8YSZ is cubic zirconia,and Y₂O₃is completely dissolved into Zr O₂.The structure of Y_0.1Ca_0.9Zr_1-xCo_xO_3-δis orthorhombic calcium zirconate,and Co₃O₄and Y₂O₃have a wide solubility in Ca Zr O₃.The electronic conductivity and total conductivity of Y_0.1Ca_0.9Zr_1-xCo_xO_3-δincrease with the increase of temperature.The increase of Co₃O₄is beneficial to the migration of oxygen ions and electrons.When x=0.3 and 0.5,the oxygen measurement range are 0-7mol%and0-15mol%respectively.The limiting current is linearly related to oxygen concentration,and increasing the Co₃O₄content and temperature can improve the oxygen measurement range of oxygen sensor.2.The Ca Zr_1-xNi_xO_3-δwas prepared by solid-state reaction method,and its structure was the orthorhombic calcium zirconate.Doping Ni O can improve the grain size and density of the sample.The increase in Ni O content has almost no effect on the activation energy of the electronic conductivity of the sample,but it can effectively reduce the activation energy of the oxygen ion conductivity.When x=0.4,Ca Zr_0.6Ni_0.4O_3-δwith high electronic conductivity and total conductivity was selected as the mixed conductor for limiting current oxygen sensor,and its oxygen measuring range was 2.1mol%-21mol%.3.The reaction mechanism of preparing Ca Zr_1-xNi_xO_3-δwith Na Cl-KCl as molten salt medium was"template-growth".When x=0.4,Ca Zr_0.6Ni_0.4O_3-δhas the highest electronic conductivity and total conductivity.The activation energy of Ca Zr_1-xNi_xO_3-δprepared by molten salt method is lower than that of Ca Zr_1-xNi_xO_3-δprepared by solid-reaction method.It shows that smaller grain size is favorable for electron migration.In addition,the oxygen measurement range of Ca Zr_0.6Ni_0.4O_3-δprepared by molten salt method is consistent with that of solid state reaction method.