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| Internal Friction on the Lithium Ion Conductor Li5La3Ta2O12 |
| WANG Weiguo1，WANG Xianping2，GAO Yunxia2，FANG Qianfeng2 |
| (1.College of Physics and Electronic Information, Yan’an University, Yan’an 716000, Shanxi， China;2. Institute of Solid State Physics, Chinese Academy of Sciences, Hefei 230031, China) |
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Abstract An investigation was made regarding the variation in internal friction and relative modulus with Li5La3Ta2O12 compound by means of force vibration. Two apparent relaxation internal friction peaks were observed. By fitting the data with two Debye peaks, the activation energy and preexponential factor of the peaks are deduced as 0.8-1.1 eV and 10-14-10-26 s, respectively, which indicates the occurrence of mutual interaction between the relaxation species (lithium vacancies). By fitting the data with the coupling model, the activation energy is deduced as 0.6-0.7 eV, close to the activation energy of lithium ion conductivity. Considering the crystal structure of Li5La3Ta2O12 compound, these two peaks are associated with the lithium ion diffusion between adjacent 48g24d sites and 48g48g sites, respectively. The peaks gradually shift toward higher temperature and increase in both height and activation energy when the sample is aged at room temperature in air. Combined with the change of sample’s mass, XRD and TGA, it can be concluded that the protons from the moisture substitute the lithium ions initially occupied the 48g sites in Li5La3Ta2O12 compound to form Li2O and new protonic derivatives, Li5-xLa3Ta2O12-x(OH)x (0<x≤2.15).
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Received: 30 March 2009
Published: 31 May 2010
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