Crystallographic facetting in solid-state reacted LiMn2O4 spinel powder

Surface facetting on lithium manganate (LiMn2O4)(2) spinel crystallites prepared via mixed oxide route has been studied by transmission electron microscopy (TEM). As-calcined powder particles from solid-state reaction at 800 degreesC for 4 h, featuring a cube-octahedral shape, exhibit facetting predominantly on {1 1 1}, {1 0 0} and {1 1 0}. The facetted planes of (1 1 1} are retained upon further annealing when others of {1 3 1}, {1 0 0} gradually mitigated, but the cube-octahedral crystal form persists even after they have been post-calcination annealed at 800 degreesC for 100 h. The {1 1 1} planes of the lowest solid-to-vapour surface energy have grown upon annealing at the expense of {1 0 0} of higher solid-to-vapour surface energy. Annealed LiMn2O4 crystallites also exhibit both the positive and negative tetrahedron, with one of which being better developed, indicating a lower symmetry space group of F43m. (C) 2001 Elsevier Science B.V. All rights reserved.