(A,Li)2Ti2O7 (A = Y、Gd) 固態電解質的製備與離子導電性研究

Preparation and ionic conductivity of (A,Li)2Ti2O7 (A = Y, Gd) solid electrolyte

謝欣諭(Shin-Yu Shieh)

指導教授 ： 高惠春

淡江大學/理學院/化學學系碩士班/碩士(2010年)

https://doi.org/10.6846/TKU.2010.00150

摘要

(A2-xLix)Ti2O7-x (A1LT, x = 0.04 – 0.11) (A = Y、Gd)，兩系列樣品分別在1150和1250 oC下燒結10 h。比較A1LT和 A2-xTi2O7 (AT)系列樣品的晶胞參數，發現在相同取代量x的情況下，A1LT系列的晶胞參數會大於AT系列的晶胞參數，這表示Li+成功的取代至A1LT樣品A site的位子。利用添加兩倍的Li2O至A1LT系列樣品，即為(A2-xLi3x)Ti2O7 (A3LT)系列，A3LT與A1LT在相同取代量x的條件下，會有相同的晶胞參數。因此，添加額外的Li2O可當作助熔劑的功用，藉由固態共熔點的產生而降低A3LT樣品的熔點，使A3LT材料獲得改善，且有較大的晶粒。添加Li2O當助熔劑至A1LT系列樣品和燒結時的溫度控制，可使(A2-xLix)Ti2O7-x (A1LT, x = 0.04 – 0.11) (A = Y 、Gd)系列在相同的燒結溫度(分別為1150和1250 oC 10 h)，樣品的相對緻密度均在90 % 以上。Y3LY系列中取代量為x = 0.06樣品在700 ℃時的導電度時為4.07 × 10-4S.cm-1;而根據報導指出，相較於Y2Ti2O7樣品在700度C的導電度為2.03X10-4S.cm-1，卻要以1600度C燒結。

關鍵字

固態電解質 ； 焦綠石結構 ； 離子導體

並列摘要

Two series of (A2-xLix)Ti2O7-x (A1LT, x = 0.04 – 0.11) with A = Y and Gd were sintered at 1150 and 1250 oC respectively for 10 h in the static air atmosphere. Unit cell a-axis of the A1LT is longer than that of the A2-xTi2O7 (AT) with the same amount of x and the same A site cation, indicating a successful substitution of the Li+ ion into the A site of A1LT. Addition of extra Li2O (2x) into A1LT, the nominal composition becomes (A2-xLi3x)Ti2O7 (A3LT), which has the same unit cell a-axis as A1LT with the same amount of x. Therefore, the extra Li2O added in the A3LT is probably acting as a self flux to lower the melting point of the mixture. As a result, materials become more compact and grains grow bigger. Adding Li2O as a flux and the heating history is carefully controlled, compact samples of (A2-xLix)Ti2O7-x (A1LT, x = 0.04 – 0.11) with A = Y and Gd with relative density higher than 90% can be obtained at a temperature as low as 1150C and 1250C respectively. One compound of Y3LT with x=0.06 prepared at 1150C had an AC conductivity of 4.07 x10-4S/cm at 700C, the ionic conductivity is comparable to a Y2Ti2O7 prepared at 1600C that is 2.03x10-4 S/cm reported.

並列關鍵字

solid state electrolyte ； pyrochlore structure ； ionic conductivity ； lithium ion ； solid oxide fuel cell ； crystal structure

參考文獻

1. J. W. Fergus, J. Power Sources 162 (2006) 30.

2. H. Inaba, H. Tagawa, Solid State Ionics 83 (1996) 1.

3. J. Molenda, K. Swierczek, W. Zajac, J. Power Sources 173 (2007) 657.

4. Z. G. Liu, J. H. Ouyang, Y. Zhou, X. L. Xia, J. Power Sources 185 (2008) 876.

5. Q. A. Huang, R. Hui, B. Wang, J. Zhang, Electrochim. Acta 52 (2007) 8144.