Research On Fabrication And Properties Of Ceria-Based Nano Solid Electrolyte And Device

Oxygen ion solid electrolytes have been widely used in various energy storage and conversion devices such as solid oxide fuel cells,oxygen sensors due to their excellent electrical properties.In comparison with state-of-the-art yttria-stabilized zirconia?YSZ?electrolyte,a ceria-based ceramic with higher electric conductivity has been proposed as a more promising candidate and expected to expand the application of micro devices in the intermediate or low temperature range?300?600??.Therefore,one-dimensional?1D?nanofibers and 2D film were prepared on the basis of ceria-based nanomaterials in this work.In order to improve the electrical properties of ceria-based electrolytes,increasing the oxygen vacancies concentration and optimizing vacancy migration process were taken into account.In addition,micro oxygen sensors which can be used in the intermediate temperature range were fabricated based on ceria-based nanofibers.The following contents are included in this work.Composite Ce_0.8Sm_0.1Nd_0.1O_1.9?SNDC?film electrolytes with aligned YSZ nanofibers were fabricated by combined electrospinning and radio frequency?RF?magnetron sputtering.The conductivity of SNDC film could be tuned by introducing of YSZ nanofibers.It is found that the film on the top of the nanofibers formed a continuous bending structure with nanofibers embedded between the substrate and the film.This specific structure induced the production of tensile strain in the horizontal direction of the film and was beneficial to the ion migration.The composite film electrolytes showed the highest conductivity of 0.026 S?cm^-1 at 600?,which is more than 2.5 times higher than that of single SNDC film.Ce_0.8Gd_0.2O_1.9?CGO?nanofibers were fabricated by electrospinning method.CGO nanofibers with different grain sizes could be obtained by controlled the calcination temperature.It is found that oxygen vacancies concentration and electrical conductivity of CGO nanofibers increased with decreasing of the grain sizes.Al₂O₃?AO?composite CGO nanofiber electrolytes were fabricated by electrospinning method.Amorphous AO was found homogeneous distribution in the composite nanofibers.With increasing AO content,the grain size of CGO decreased from 10.8 nm to 4.2 nm and the oxygen vacancies concentration increased.The conductivity of the CGO/AO composite electrolytes had a sharp growth in the beginning and reaches the maximum at 0.005 mol,then drops rapidly.This phenomenon was due to the combined effect of oxygen vacancies and amorphous AO.Moreover,the addition of AO in the com posite nanofibers could suppress the grain growth of CGO grains in the elevated temperature.After calcined at high temperature,the grain size of CGO/AO composite nanofibers were smaller than that of CGO nanofibers.What'more,the composite nanofibers had the high oxygen vacancies concentration and temperature stability.Composite YSZ film electrolytes with aligned CGO nanofibers were prepared by combined electrospinning and spin coating methods.Micro oxygen sensors were designed and fabricated based on the composite electrolytes.It is found that the micro oxygen sensors showed high conductivity.Furthermore,the operation temperature of oxygen sensors based on the composite electrolyte is decreased by 350? relative to the sensors based on YSZ or CGO bulk electrolyte.