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Lithium tantalum oxide, LiTaO3, with an average particle size in the µm range is known as a very poor Li ion conductor. It is shown here that its Li conductivity can be drastically increased by ball milling. The so-obtained nanostructured powder with an average particle size of about 20 nm shows a dc conductivity, σdc, of about 3 × 10−6 S cm−1 at T = 450 K (σdcT = 1.4 × 10−3 S cm−1 K) which is about 5 orders of magnitude larger than that of the corresponding microcrystalline powder at the same temperature. The activation energy EA is reduced by about one-third, i.e., it decreased from EA = 0.90(1) eV to about EA = 0.63(1) eV. The effect of different milling times on the ionic conductivity is studied. Furthermore, the thermal stability of the nanocrystalline materials against grain growth has been examined by in situ impedance spectroscopy. Interestingly, the Li conductivity of a sample milled for 16 h does not change much even when the material is exposed to about 700 K for several hours. Moreover, the Li self-diffusion in the nanostructured as well as the coarse grained materials has been investigated by various solid-state 7Li NMR techniques.
Wilkening et al. (Fri,) studied this question.