Li6ALa2Nb2O12 (A=Ca, Sr, Ba): A New Class of Fast Lithium Ion Conductors with Garnet-Like Structure
Li6ALa2Nb2O12 (A=Ca, Sr, Ba): A New Class of Fast Lithium Ion Conductors with Garnet-Like Structure
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DOI：
10.1111/j.1551-2916.2005.00060.x
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发表时间：
2005-02
影响因子：
3.9
通讯作者：
V. Thangadurai;W. Weppner
中科院分区：
文献类型：
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作者：
V. Thangadurai;W. Weppner
以适量的金属氧化物、硝酸盐和氢氧化物为原料，通过固相反应制备了通式为Li 6Ala 2Nb 2 O 12（A=Ca，Sr，Ba）的石榴石状金属氧化物。X射线粉末衍射数据表明，Li 6Ala 2Nb 2 O 12化合物与母体化合物Li 5La 3 Nb 2 O 12是同构的。立方晶格参数被发现，增加碱土金属离子的尺寸。在相同的制备条件下，随着稀土元素取代La，晶粒尺寸显着减小。Ca取代的化合物表现出对总电阻的体电阻和主要晶界贡献，而Sr和Ba取代的化合物主要表现出体电阻，具有相当小的晶界贡献（在20°C下占总电阻的约14%），并且随着温度的升高而进一步降低。相比之下，离子电导率随着碱土元素离子半径的减小而减小。在所研究的化合物中，Ba化合物Li 6 BaLa 2Nb 2 O 12在室温（22°C）下显示出最高的离子电导率6 × 10−6 S/cm，最低的活化能为0.44 eV，而相应的Ca和Sr化合物分别为0.55和0.50 eV。离子电导率与母体Li 5La 3 Nb 2 O 12和迄今已知的其他快锂离子导体的离子电导率相当。
Garnet-like structured metal oxides with the general formula Li6ALa2Nb2O12 (A=Ca, Sr, Ba) have been prepared by solid-state reaction using appropriate amounts of corresponding metal oxides, nitrates, and hydroxides. The powder X-ray diffraction data reveal that Li6ALa2Nb2O12 compounds are isostructural with the parent compound Li5La3Nb2O12. The cubic lattice parameter was found to increase with increasing size of the alkaline earth ions. The grain size decreases considerably with the substitution of La by the alkaline earth elements under the same preparation conditions. The Ca-substituted compound exhibits both bulk and major grain boundary contributions to the total resistance, while the Sr- and Ba-substituted compounds show mainly bulk resistance with a rather small grain boundary contribution (∼14% of the total resistance at 20°C) with further decrease with increasing temperature. In comparison, the ionic conductivity decreases with decreasing ionic radius of the alkaline earth elements. Among the investigated compounds, the Ba-compound Li6BaLa2Nb2O12 shows the highest ionic conductivity of 6 × 10−6 S/cm at room temperature (22°C) and lowest activation energy of 0.44 eV compared with 0.55 and 0.50 eV for the corresponding Ca- and Sr- compounds, respectively. The ionic conductivity is comparable with that of parent Li5La3Nb2O12 and other fast lithium ion conductors known so far.