Synthesis and structures of the partially ordered rock salt phases, Li3M2XO6: MMg, Co, Ni; XNb, Ta, Sb

Abstract

The crystal structures of four rock salt superstructure phases, Li₃M₂XO₆(M₂X Ni₂Nb, Ni₂Ta, Co₂Ta and Mg₂Nb) have been refined by X-ray and/or neutron powder diffraction; three members of this family were synthesized for the first time, M₂X Ni₂Nb, Ni₂Sb and Co₂Ta. All have similar rock salt superstructures but with partial order only, over three sets of octahedral sites, of the cations M₂X. Differences in the distributions of site occupancies are discussed.