近年來固態氧化物燃料電池為高度關注之能源轉化元件，然而其運作溫度高(800~1000 OC)為商業化之一大挑戰，高運作溫度(800~1000 OC)限制元件材料之選擇，必須搭配其他昂貴的陶瓷或超合金零組件，也因高溫導致材料組成的變化、元素損失、相互反應和電極微結構破壞，最終降低元件性能甚至故障，降低操作溫度(400~700 OC)成為了固態氧化物燃料電池下一世代積極發展的技術。為了降低操作溫度，低溫下具有高導電性的氧化鈰- 碳酸鹽的複合電解質成為了具發展潛力的材料，與常用的電解質相比具有優良的離子導性和獨特的雙離子導電行為，本研究主要目標是通過開發氧化鈰- 碳酸鹽複合電解質材料提高固態氧化物燃料電池在低溫範圍（400-700 OC）的性能。研究中以多孔氧化鈰作為基材，滲入鋰/鈉碳酸鹽形成複合電解質，增強的離子導電率和界面傳導機制。
本研究中主要探討以不同碳酸鹽含量，對複合電解質中離子導電度在低溫範圍（400-700 OC）的影響，以及在相近的碳酸鹽含量下其不同之兩相界介面面積大小對複合電解質中離子導電度在低溫範圍（400-700 OC）的影響，藉由這些實驗更能清楚了解複合電解質對電性的影響及反應機制。

In the recent years, the solid oxide fuel cell(SOFC) has received great attention as an efficient energy conversion device. However, the high working temperature (800~1000OC) for SOFC is a challenge for commercialization. Due to the high working temperature(800~1000OC) for SOFC, the materials of cell components are limited to precious metals or expensive ceramics. At the high temperature, it also causes phase changing, chemical reaction and corrosion. As result, the performances of fuel cell gradually degrades. Therefore, intermediate -temperature solid oxide fuel cells (IT-SOFCs) are proposed for lower working temperature (400~700OC) than current state of the art SOFCs. If the working temperature is reduced, most problems may be solved. In order to reduce the operation temperature, high conductivity ceria-carbonate composites may be a promising electrolyte candidates for intermediate temperature solid oxide fuel cells (IT-SOFCs), because of its impressive ionic conductivity and unique hybrid ionic conduction behavior compared to the commonly used single-phase electrolyte material. The main objective of this study is to improve the performance of SOFC at low temperature range (400-700OC) by using ceria–carbonate composite material. The approach of composite electrolyte involves using a ceria-based for the matrix material with the infiltration of the carbonates. The electrical conduction of composite electrolyte was contributed by the migration of oxygen ions in solid state and carbonate ions in liquid state. It was observed that the two-phase electrolytes exhibit coionic (O=/H+) conductors during fuel cell operation under the H2/ air atmosphere. It is believed that highly mobile ions at the interface between doped ceria and carbonates may contribute to the high conductivity of the composite electrolyte. In other words, the super-ionic phase might exist at the interface between doped ceria and carbonates, where the defect concentrations are high. Thus, the electrical conduction of composite electrolytes with various types of microstructures were evaluated at temperatures ranging from 300OC to 700OC. For powder mixture, the composite samples were prepared by direct mixing of doped ceria and carbonate powders. For infiltrated composite, the carbonates were infiltrated into porous ceria substrates at 650OC. SEM, XRD, and Electrochemical Impedance Spectroscopy were employed to conduct microstructural, structural and impedance analyses. The electrical conduction behavior of composite electrolytes will be rationalized based on the pore size, pore distribution and interface area.

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