新型锂离子导体Li5La3Ta2O12的内耗

采用低频内耗仪，以强迫振动方法测量了锂离子导体Li₅La₃Ta₂O₁₂在升温过程中的内耗和相对模量，并结合晶体结构分析其形成机制.结果表明：在大气环境的升温过程中，Li₅La₃Ta₂O₁₂出现2个明显的弛豫型内耗峰，其弛豫元（锂空位）之间存在相互作用，由Debye峰拟合得到其激活能和弛豫时间指数前因子分别为0.80～1.00 eV和10-14～10-26 s，利用耦合模型处理得到弛豫峰的激活能约为0.60～0.70 eV，与锂离子电导率的激活能（0.50～0.60 eV）接近；2个弛豫型内耗峰分别对应于锂离子在相邻四面体和八面体间（24d48g）以及相邻八面体间（48g48g）的扩散；随着Li₅La₃Ta₂O₁₂在空气中的放置时间增加，其内耗峰逐渐向高温区域移动，且其峰高度和激活能逐渐增大；Li₅La₃Ta₂O₁₂经室温时效处理后，水进入其晶格替代Li₂O而形成新的锂离子化合物Li₅-xLa₃Ta₂O1₂-x(OH)x（0

Internal Friction on the Lithium Ion Conductor Li5La3Ta2O12

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 pre exponential 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 48g24d sites and 48g48g 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