摻雜型氧化鈰基螢石材料用於中溫固態燃料電池電解質之研究

Abstract

由於先前的研究觀察到錳鈷摻雜之鉍鐵基陰極在氧化鈰材料有界面擴散現象，因此本研究探討三元鉍、錳、鐵共摻雜之氧化鈰螢石材料之合成特性與導電性表現。在本研究中，以EDTA-檸檬酸法合成不同摻雜量的粉末，利用X光繞射法確定不同元素摻雜之固溶極限，用掃描電子顯微鏡進行燒結之微結構分析，利用能量散射光譜進行定量成分分析，探究高溫重量損失之成分變化。導電性方面利用兩點式直流和交流阻抗頻譜量測(EIS)，以EMF法來測量離子傳導係數，以熱重分析(TGA)探討材料之導電性及氧成分的非當量比。結果顯示鉍的固溶極限為8-9 at%，而錳、鐵的固溶量則少於1 at%。鉍錳鐵共摻雜之氧化鈰粉末(811、9HH)乾壓生胚可藉由在830 oC持溫3小時、1050 oC和1100 oC持溫1小時以上進行燒結，密度高於98%相對密度。導電度結果顯示在800 oC時，811與9HH之總導電率分別為3.63x10-3 Scm-1和1.62x10-3 Scm-1。EIS結果顯示在400 oC以上，9HH之導電機制為離子傳導為主，在600 oC之離子傳導係數(ti)可達到0.98。

From previous research, a diffusion reaction was observed at the interface of manganese and iron co-doped bismuth-iron based cathode and ceria-based material. Therefore, in this study, the effects of bismuth, manganese and iron co-doping in ceria-based fluorite (CeO2) have been investigated. The powders were synthesized by EDTA-citrate method. The solubility limits of dopants were determined by X-ray diffraction (XRD). SEM and EDS were carried out to analyze the microstructure and composition after sintering. The conductivity was measured by 2-probe DC and AC impedance methods, the ionic transference number was evaluated by EMF method and the oxygen nonstoichiometry was analyzed by thermogravimetric analysis (TGA). The results show the solubility limit of Bi is 8-9 at% and less than 1 at% for Mn and Fe. The die-pressed green bodies of ceria-based powders, 811 and 9HH, can be crystalized at 830 oC for 3 h and sintered at 1050 oC -1100 oC for 1 h to get dense samples. The electrical conductivities show that 811 and 9HH have the highest electrical conductivity at 800 oC, 3.63x10-3 Scm-1 and 1.62x10-3 Scm-1, respectively. The ionic transference number of 9HH evaluated by EIS method is higher than 0.9 at 400 oC, and reached 0.98 at 600 oC.