摘要
本研究主要提出氧化釓摻雜氧化鈰(Gadolinia-doped Ceria, GDC)薄膜於固態氧化物燃料電池中固態電解質層應用的可行性評估。GDC薄膜係以射頻反應性濺鍍法(RF-Reactive Sputtering)成長於商業化氧化鋁基板及NiO-GDC基板上，並藉由觀察O2/Ar流量比與退火溫度對GDC薄膜之沈積速率、表面型態、結晶結構以及離子傳導率之影響，以尋求符合中低溫型固態氧化物燃料電池中固態電解質層的需求。
由實驗結果所顯示的O2/Ar流量比效應發現，GDC薄膜之表面結構隨著O2/Ar流量比的增加而有柱狀結構(Columnar Structure)的產生，且薄膜之結晶結構亦逐漸由未完全氧化之(Ce,Gd)Ox結構轉變為完全氧化之GDC立方螢石結構。
由實驗結果所顯示的退火溫度效應發現，GDC薄膜在經過700°C兩小時的退火處理後，其在初沈積薄膜中所觀察到屬於未完全氧化之(Ce,Gd)Ox結構，已在退火處理後完全氧化為GDC立方螢石結構；且當退火溫度增加至900°C時，原本在高氧氣流量的條件下所發現之柱狀結構已完全消失並轉而形成ㄧ平坦且緻密之結構；然而，在退火溫度再增加至1100°C時，薄膜則因為其熱膨脹係數與基材之差異過大，因而造成薄膜表面有不規則裂痕的產生。
由交流阻抗分析儀(AC impedance)分析經退火處理後之電解質薄膜可以發現，退火溫度為700°C時，隨著氧氣流量的增加，薄膜之氧離子傳導率隨之下降，且其傳導模式隨著氧氣流量的增加而逐漸由晶粒傳導為主之機制轉為由晶界傳導為主之機制；在退火溫度增加至900°C時，其氧離子傳導率在所有的氧氣流量條件下均較退火溫度700°C高，且其傳導模式亦隨著退火溫度的增加而轉以晶粒傳導為主之機制；在退火溫度為1100°C時，則因為薄膜有裂縫之產生，因而導致氧離子傳導率的下降，使其傳導模式再度轉以晶界傳導為主之機制。

關鍵字：固態氧化物燃料電池、氧化釓摻雜氧化鈰、射頻反應性濺鍍法

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

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