摻雜對磷灰石結構鍺酸鑭基電解質應用於固態氧化物燃料電池之特性 影響研究

A Study of Doped Lanthanum Germanate-Based Electrolytes for Solid Oxide Fuel Cell Applications

林婉茹(Wan-Ju Lin)

指導教授 ： 徐永富 ； 王錫福

國立臺北科技大學/工程學院/材料及資源工程系研究所/碩士(2012年)

摘要

本研究是利用固態合成法製備磷灰石結構鍺酸鑭基SOFC電解質材料，主要是利用摻雜半徑較大的離子取代La9.5Ge6O25.25中部分Ge4+，藉以開發最佳導電率之電解質材料，希望能夠取代8YSZ。本實驗將La9.5□0.5(GeO4)6O2±y分別摻雜Al2O3、MnO2、MoO3、TiO2、WO3、Ga2O3、Nb2O5、Fe2O3、NiO、SnO2及MgCO3，透過固態合成法製備鍺酸鑭基電解質粉末。配合不同的摻雜劑利用不同的製程參數進行燒結，並測量其電性，期望能找出最佳成分配比及製程條件。研究結果發現，微量摻雜MnO2導致燒結緻密化溫度過高、摻雜TiO2有二次相生成，而摻雜NiO造成導電率過低，因此此三種摻雜劑不利應用於鍺酸鑭基電解質材料。其他摻雜組成如La9.5Ge5.5Al0.5O26、La9.5Ge5.5Mo0.5O26.75、La9.5Ge5.5W0.5O26.75及La9.5Ge5.5Fe0.5O26、La9.5Ge5.5Nb0.5O26.5導電率較佳，在量測溫度800oC時導電率和8YSZ相近，其中又以La9.5Ge5.5Nb0.5O26.5在量測溫度為800oC時，具有最佳導電率(0.045 S/cm)。

關鍵字

磷灰石 ； 固態氧化物燃料電池 ； 鍺酸鑭 ； 電解質

並列摘要

The purpose of this study was to develop apatite-type lanthanum germanate-based solid electrolytes for SOFC (Solid Oxide Fuel Cell). In order to achieve the best conductivity of the electrolyte materials applications, these ceramics were doped with various ions with larger ionic radii than that of Ge4+ ion and to substitute part of the ion Ge4+ in La9.5Ge6O25.25. Various dopants including Al2O3、MnO2、MoO3、TiO2、WO3、Ga2O3、Nb2O5、Fe2O3、NiO、SnO2 and MgCO3 were added into to La9.5□0.5(GeO4)6O2±y, respectively. These lanthanum germanate-based solid electrolyte powders were synthesized by solid state reaction. These specimens were sintered at various temperatures and periods of time, then the conductivity of the specimens were measured. The results showed that, sintering temperature is too high for achieve the desired densities by doping MnO2, secondary phase is formed by doping TiO2, the electrical conductivity is reduced significantly by doping NiO. Therefore, the three kinds of dopant were unfavorable used in the lanthanum germanate-based electrolytes. However, other doped specimens such as La9.5Ge5.5Al0.5O26, La9.5Ge5.5Mo0.5O26.75, La9.5Ge5.5W0.5O26.75, La9.5Ge5.5Fe0.5O26 and La9.5Ge5.5Nb0.5O26.5 have better conductivity, which are similar to that of 8YSZ measured at 800oC. Among them La9.5Ge5.5Nb0.5O26.5 possesses the best conductivity (0.045 S/cm) at 800oC.

並列關鍵字

apatite ； SOFC ； lanthanum germanate ； electrolyte

參考文獻

[2] B.C.H. Steele and A. Heinzel, "Materials for fuel-cell technologies," Chemistry of Nature, vol 414, 2001, pp. 345-352.

[5] P.R. Slater, J.E.H. Sansom and J.R. Tolchard, "Development of Apatite-Type Oxide Ion Conductors," Chemistry Record, vol 4, no 3, 2005, pp. 373-384.

[6] J.B. Goodenough, "High oxide ion conductivity in Al-doped germanium oxyapatite," Annual Review of Materials research, vol 33, 2003, pp. 91-128.

[7] K.R. Kendall, C. Navas and J.K. Thomas, "Recent developments in perovskite-based oxide ion conductors," Solid State Ionics, vol 82, 1995, pp. 215-223.

[8] S. Nakayama, H. Aono and Y. Sadaoka, "Ionic conductivity of Ln10(SiO4)6O3 (Ln = La, Nd, Sm, Gd and Dy," Chemistry Letters, vol 24, 1995, pp. 431-432.