Lithium-Containing Garnets

The garnet structure has shown itself to be remarkably flexible in accommodating not only a compositionally diverse range of elements and oxidation states, but also the ability to incorporate considerable 

Variable temperature neutron diffraction experiments have shown that the [La3Ta20i2] sublattice is fully ordered and appears typical for a robust, dense, framework material, thus indicating that a hopping model for lithium ion mobihty is operative in these compounds, rather than a more cooperative model, as observed in some systems such as U2SO4. However, the presence of a complex distribution of lithium cations in these fast ion conducting phases has made it difficult to identify which 

The identification of the pathway for lithium migration through the garnet structure provides the necessary information for optimising the conductivity of these phases. However, a number of additional features have been observed in some garnets that are incompletely understood and 

In addition to showing this unusual structural effect, the compounds LisLn ShzOiz Ln = La, Pr, Nd, Sm, Eu) also showed a temperature dependence in the activation energy with a gradual change in gradient in the Arrhenius plot between 200 °C and 300 It has been 

vanWiillen, T. Echelmeyer, H.-W. Meyer and D. Wilmer, Phys. Chem. Chem. Phys., 9, 3298 (2007). 

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Regarding ceramic-containment materials," sihca, SiO, and alumina, Al O, are strongly attacked and hence readily dissolve in liquid lithium. By contrast, alkaline-earth oxides such as beryllia (BeO), magnesia (MgO), and calcia (CaO) and rare-earth oxides such as ceria (CeOJ, yttria (YfiJ, chromite spinel (FeCr OJ, and yttrium aluminum garnet (Y AljOj ) seem to be noncorroded below 500 C, while aluminum, titanium, and zirconium nitrides or... 

Whilst the fast lithium mobility in these compounds was determined it was unclear what the mechanism for lithium conduction would be. Examination of the [La3Ta20i2] framework shows that there is a considerable amount of extra-framework space and that three distinct interstices that could function as lithium coordination sites are available. As shown in Figure 3.25 the structure contains six distorted oxide octahedra and two square prisms in addition to the three tetrahedral interstices that are fully occupied in the conventional garnet stoichiometry. Some initial reports indicated that lithium was found exclusively on the distorted octahedral sitej but a series of neutron diffraction experiments identified a complex arrangement of lithium across both the oxide tetrahedra and octahedra. ... 

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