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.