(M2-xLi3x)Ti2O7 (M = Gd、Y) 離子導體的製備、結構和特性研究

Preparation, Structure and Properties of M2-xLi3xTi2O7 (M = Gd, Y) Ionic Conductors

蘇文彬(Wen-Pin Su)

指導教授 ： 高惠春

淡江大學/理學院/化學學系碩士班/碩士(2005年)

https://doi.org/10.6846/TKU.2005.00781

摘要

本實驗以固態法製備兩系列含有鋰離子的氧化物，樣品起始組成為(M2-xLi3x)Ti2O7 (M = Gd、Y)。所得到Gd 與Y 系列單相樣品的取代範圍分別為x = 0.04 - 0.11和x = 0.05 - 0.10 的焦綠石結構，屬立方晶系，空間群為Fd3m。在相同的製備溫度下，樣品的晶胞大小不會隨取代量x 的改變而有變化，並且在製備的過程中，其鋰離子逸失的量皆小於5%。燒結完成後的樣品緻密度隨著取代量x 的增加而增加，大約在50% - 60%之間。在交流阻抗頻率為104 - 106 Hz 的量測條件下，樣品在105.5 Hz 時皆有最好的導電度。Gd 系列中取代量x = 0.11 樣品在室溫與900℃時的導電度分別為1.23 × 10 3 S•cm-1 和1.03 × 10 2 S•cm-1 活化能分別為 5.23 meV 和 30.4 meV。在Y 系列中取代量x = 0.10樣品在室溫與900℃時的導電度分別為8.00 × 10-3 S•cm-1 和1.00 × 10-3 S•cm-1，活化能分別為 0.510 meV 和 62.42 meV。隨著Gd 與Y 的莫耳比例減少，樣品的離子導電度增加。相同的鋰離子取代量，Gd 系列樣品的離子導電度皆高於Y 系列的樣品。

關鍵字

固態電解質 ； 焦綠石結構 ； 離子導電性 ； 鋰離子 ； 固態燃料電池 ； 晶格結構

並列摘要

In this research, two series of oxides containing lithium ion were prepared with nominal composition of M2-xLi3xTi2O7 (M = Gd, Y) by a solid state reaction method. Single phase materials with pyrochlore structure were found in a solubility range of 0.04 ~x ~0.11 for M = Gd and 0.05 ~x ~0.10 for M = Y. The amount of lithium ion vaporized away in the preparation process is less than 5%. Density of the sintered pellet is about 50% ~ 60% of the unit cell density. All the samples have a cubic symmetry with a space group of Fd3m. Unit cell volume does not change with the amount of Lithium ion substitution. Ionic conductivity was measured in 104 ~106 Hz frequency range. All of the samples have the highest AC impedance found at a frequency of 105.5 Hz. For the Gd2-xLi3xTi2O7 series, x = 0.11 sample has the highest ionic conductivity. At room temperature and 900℃,they are 1.23 × 103 S•cm1 and 1.03 × 102 S•cm1, respectively. Activation energy observes with respect to the room temperature and high temperature ranges are 30.40 meV and 5.23 meV. For the Y2-xLi3xTi2O7 series, x = 0.10 sample has the highest ionic conductivity. At room temperature and 900℃,they are 1.00 × 103 S•cm and 8.00 × 103 S•cm1, respectively. Activation energy observes with respect to the room temperature and high temperature ranges are 62.42 meV and 0.51 meV. Ionic conductivity increases with the decreasing of the Gd and Y molar ration. Ionic conductivity of Gd series samples are always higher than that of the Y series samples with the same amount of lithium ion doping.

並列關鍵字

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

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