(鐵、鈣)參雜氧化鈰(釤)基電解質之燒結性、微結構及電性研究

Investigation on Sintering, Microstructure, and Electrical Conductivity of (Ca,Fe)-Sm Doped Ceria Electrolytes

張子泓(Zi-Hong Chang)

指導教授 ： 韋文誠

國立臺灣大學/工學院/材料科學與工程學研究所/碩士(2020年)

https://doi.org/10.6342/NTU202002961

摘要

本研究旨在探討釤、鈣、鐵共摻雜二氧化鈰基電解質之材料合成、燒結性、微結構及電性分析。首先以 EDTA-檸檬酸法合成兩系列共六種二氧化鈰基電解質粉末：SDC10 (Ce0.9Sm0.1O2-δ)；SDC15 (Ce0.85Sm0.15O2-δ)；SDC20 (Ce0.8Sm0.2O2-δ)；SDC18-C (Ce0.8Sm0.18Ca0.02O2-δ)；SDC18-C/F (Ce0.8Sm0.18Ca0.01Fe0.01O2-δ)；SDC18 -F (Ce0.8 Sm0.18Fe0.02O2-δ)，上述六種粉末透過X光繞射分析得知皆為單一立方螢石結構。SDC系列樣品在1500 °C燒結8小時達98%理論密度，而鐵、鈣摻雜SDC樣品則可在1250 °C燒結8小時達96%理論密度，掃描式顯微鏡分析結果顯示鈣參雜的SDC樣品會於晶界上生成矽酸鈣第二相，達到清理晶界雜質的效果；而穿透式顯微鏡分析結果則顯示SDC系列樣品晶界附近有釤的聚集。以兩點式量測法及交流阻抗分析量測樣品之導電率、活化自由能(Ea)，可發現SDC系列樣品中以SDC20在空氣環境700 °C時有最高的電導率2.17*10-2 S·cm-1，而參雜的SDC系列樣品中則以SDC18 -C/F在空氣環境700 °C時有最高的電導率3.95*10-2 S·cm-1，交流阻抗頻譜顯示電性的優化主要來自於晶界電阻的下降，和晶粒內電阻較無關，此外，晶界處的電荷聚積和釤的聚集有詳細的分析討論。

關鍵字

氧化鈰 ； 導電性 ； 燒結性 ； 釤 ； 鈣 ； 鐵 ； 聚集

並列摘要

The sinterability, microstructure and conductivity of Sm, Ca and Fe multi-doped ceria were investigated in this study. Two series, including six ceria-based powders were synthesized by EDTA-citric method: They are SDC10 (Ce0.9Sm0.1O2-δ), SDC15 (Ce0.85Sm0.15O2-δ), SDC20 (Ce0.8Sm0.2O2-δ), SDC18-C (Ce0.8Sm0.18Ca0.02O2-δ), SDC18-C/F (Ce0.8Sm0.18Ca0.01Fe 0.01O2-δ) and SDC18-F (Ce0.8 Sm0.18Fe0.02O2-δ). The density of SDC samples achieved 98% T.D. after sintering at 1500 °C for 8 h, but that of M-doped SDC samples achieved 96% T.D. after sintering at 1250 °C for 8 h. SEM analysis showed the formation of calcium silicate compounds which cleaned the SiO2 impurity (called “scavenging effect”) on the grain boundaries for Ca-doped ceria. TEM analysis confirmed the phenomenon of Sm-segregation near the grain boundary for SDC samples. The conductivity and activation energy (Ea) of all samples were measured by both two-probe measurement and electrochemical impedance spectroscopy (EIS). The results showed that SDC20 and SDC18-C/F performed a conductivity of 2.17*10-2 S·cm-1 and 3.95*10-2 S·cm-1 at 700 °C, respectively. AC impedance spectra showed the improvement of conductivity was attributed by the significant decrease of RGB value. The charging effect and model at the grain boundary and the Sm-segregation are studied and discussion in details.

並列關鍵字

CeO2 ； conductivity ； sintering ； Sm ； Ca ； Fe ； segregation

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