Fabrication Of Sc₂O₃Stabilized ZrO₂Solid Electrolyte

The choice and fabrication of solid electrolyte are imperative for the operation of solid oxide fuel cells (SOFC). Oxide-ion conductors are most commonly investigated as electrolyte materials for SOFCs. Amongst them, ZrO2-based oxides are at the center of research for their high oxide ionic conductivity, good chemical stability, and potential for utilization in a wide variety of fields. Traditionally, YiO3-stablized ZrO2is commonly used as an electrolyte for SOFCs, yet its instability and insufficient ionic conductivity negatively affect its efficiency. This work studies a new type of electrolyte material, Sc2O3-stablized ZrO2, and investigates its fabrication techniques and properties.The electrolyte materials,(Sc2O3)x(ZrO2)1-x, are fabricated by a sol-gel technique. Thermogravimetric (TG) and differential scanning calorimetry (DSC) analyses of the xerogel precursor were carried out. From changes in enthalpy and weight of the precursor, a relatively weak endothermic peak and weight loss of11.8%were found at222℃, primarily due to the vaporization of water in the precursor and decomposition of organic solvents. At262℃, a wide exothermic peak and weight loss of40%were found due to the dissociation and combustion of organic component, as well as the formation of amorphous ZrO2in the process.X-ray diffraction (XRD) analysis and particle size analysis, and determination of coefficient of thermal expansion of (Sc2O3)x(ZrO2)i-x were further carried out. From the XRD analysis, it was discovered that as the concentration of Sc2O3in ScSZ increases, the sample structure changes from monoclinic ZrO2to tetragonal and cubic ZrO2. ScSZs with8-10mol%Sc2O3are predominantly in the tetragonal and cubic phase, due to Sc2O3stabilized ZrO2. The particle size analysis showed that an average particle size of (Sc2O3)x(ZrO2)i-x electrolyte powders is about0.7μm, and an uniform distribution of particle size.An electrical conductivity of (Sc2O3)x(ZrO2)1-x electrolyte was measured by an AC impedance technique. The experimental results showed that when temperature increases, conductivity of ScSZ electrolyte increases with the temperature increases (a maximum conductivity of0.0952S/cm at800℃). The activation energy of electrolyte decreases as the concentration of Sc2O3increases. The microstructure of (Sc2O3)x(ZrO2)1-x electrolyte sintered at different temperature showed that grain size increases and compactness improves as sintering temperature increase. At same sintering temperature, the compactness of electrolyte increases as SC2O3doping concentration increasing.The microstructure, morphology and electrochemical properties of ScSZ with lmol%Bi2O3sintered at different temperature were investigated. In XRD pattern, Bi2O3diffraction peak was not found, which indicated a solid solution of Bi2O3with ZrO2formation., At sintering temperatures above1400℃, the sinter bodies of1BilOScSZ has already reached density. An electrical conductivity of1BilOScSZ sintered at1400℃was0.0627S/cm at800℃, and an activation energy of1BilOScSZ sintered at1400℃was98.6kJ/mol.