Structural phase transition of the spinel-type oxide LiMn 2O 4

Abstract

The crystal structure of the low-temperature (LT) form of spinel-type LiMn 2O 4 has been studied by neutron and X-ray powder diffraction as well as electron diffraction. Reflections of the LT phase in its neutron and X-ray diffraction patterns were indexed on the basis of not a tetragonal unit cell but roughly an orthorhombic one (space group Fddd) with lattice parameters a=8.2797(2), b=8.2444(3) and c=8.1981(2) Å. However, the presence of extra reflections which cannot be indexed with this unit cell shows that the actual lattice parameters are different from the above ones. Superlattice reflections, which were missing in powder diffraction patterns, with tripled periodicity were observed in electron diffraction patterns of the LT phase.