LISICON and Related Phases

The introduction of vacancies into lithium germanate or silicate can be illustrated by two substitutions. The replacements  

Initial studies focused on the effect of introducing pentavalent cations into the structure and the phase behaviour of systems such as Li3+xXi xSi 04 (X = P, As, The behaviour of these materials 

It should be remembered that the structure is derived from neutron diffraction experiment and, as for all diffraction experiments, it represents a time-averaged summation through space of the contents of multiple unit cells. In the case of a fully ordered structure, such as that of room temperature phase of lithium phosphate, the averaging process is not apparent in the resulting structural model. However, in the case of 

The first of these arrangements has the same structure as the stoichiometric material Li2ZnGe04, a fully ordered material that is isostructural 

If two Type-I clusters exist in adjacent portions of the lattice then further vacancy ordering can occur around another octahedrally coordinated site that shares four faces with tetrahedral positions that are fully occupied in Li2ZnGe04. Two of these tetrahedra contain vacancies and the cations are displaced in a manner that suggests that they are not occupied simultaneously with the central octahedron. This arrangement of a central occupied octahedron linked via shared faces with two full and two empty tetrahedral interstices is a Type-II cluster. 

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