Gadolinia-doped Ceria Solid Electrolyte Thin Films Prepared by RF Reactive Sputtering and Its Annealing Behavior

• Main Authors: Yong-siou Chen, 陳永修
• Other Authors: Chia-Pyng Lee
• Format: Others
• Language: zh-TW
• Published: 2008
• Online Access: http://ndltd.ncl.edu.tw/handle/60673152149351808355

碩士 === 國立臺灣科技大學 === 化學工程系 === 96 === Abstract This study is to evaluate the feasibility and application of Gadolinia-doped Ceria (GDC) thin films as solid electrolyte for Solid Oxide Fuel Cells (SOFCs). GDC thin films were deposited on commercialized alumina substrates and NiO-GDC substrates by RF reactive sputtering in various O2/Ar flow ratio and then treated with the thermal treatments. Experiment results indicated that the deposition rate, surface morphology, crystalline structure, and ionic conductivity of the deposited films depend on the O2/Ar flow ratio and annealing temperatures. Our results showed the surface morphology of as-deposited GDC thin films were found to be an assembly of columnar crystallites and the crystalline structure was varied from incompletely-oxidized (Ce,Gd)Ox to completely-oxidized GDC as increasing the O2/Ar flow ratio. GDC thin films were cubic fluorite structure as the annealing temperature was 700°C, and surface morphology became denser as increasing upto 900°C. However, when the annealing temperature was raised up to 1100°C, cracks on the surface of GDC thin films were apparently observed because of the thermal expansion conefficient mismatch between GDC films and alumina substrate. The governing mechanism of conduction of annealed GDC thin films were mainly dominated by grain contribution at lower oxygen flow rate when the annealing temperature was 700°C, while the mechanism was gradually chaged to grain boundary contribution with deacresing the ionic conductivity at higher oxygen flow rate. At 900°C, the governing mechanism of conduction of annealed GDC thin films were changed to grain contribution with increasing the ionic conductivity. However, when the annealing temperature was raised to 1100°C, the governing mechanism of conduction of annealed GDC thin films were changed to grain boundary contribution with the lower ionic conductivity because of the existence of the cracks on surface. Keywords：Solid Oxide Fuel Cells (SOFCs), Gadolinia-doped Ceria (GDC), RF reactive sputtering