The crystal structure of Li3Sb04 has been determined by analogy with Na,BiO,, and refined by the RiFtveld method using X-ray powder diffraction data. It is monoclinic, space group P2/c, a = 5.1579(2), b= 6.0922(3), c=5.1397(2) A, B= 108.839(4)". The structure is an ordered rocksalt type, with distorted M 0 6 octahedra.The crystal structure of Li,SbO, was first examined by Blasse using X-ray powder diffraction (XRD) d?ta.' The unit cell was given as tetragonal, a = 6.12, c = 8.50 A; the structure was suggested to be an ordered rocksalt structure, where a = $4 and c = 2aR (aR =unit cell of rocksalt). The Sb atoms were estimated to be located in positions ($ 3 0), (+ $), (a + 3) and (3 1 $) within a cubic close-packed (ccp) oxide array, giving a cation order related to that of spinel. Based on the Sb-0 framework, the agreement between observed and calculated intensities was reasonably good, with an R factor of 12%.The powder pattern of Li,SbO, given in the powder diffraction file (card no. 17-824)2 was found to match that of Li2Te04 (card no. 26-8$1),, which has a similar unit cell with a=6.045 and c = 8.290 A. The structure of Li2Te04 was determined in the space group P4,22, and was found to be a distorted inverse spinel with Te in octahedral sites and Li in both tetrahedral and octahedral sites., In spite of the similarity between the XRD patterns of Li,SbO, and Li2Te04, it seemed unlikely, from its stoichiometry, that Li3Sb0, could have a spinel structure. Since, however, the XRD patterns of both Li3Sb04 and Li2Te0, would be dominated by the scattering powers of Sb and Te, respectively, the similarity between the two patterns may confirm Blase's observation of a spinel-like cation arrangement .Other Li,MO, structures with similar-sized M atoms to Sb are Li,NbO, and Li,TaO,; these belong to the rocksalt family, with ordered Na,Ta04 and Na,Nb04 also have rocksalt-related structures and can exhibit both order and disorder of the cations, in different polymorphs. lO,ll The XRD pattern of Li,SbO, was examined as part of an investigation into rocksalt-related phases in the system Li,SbO,-CuO. Although the XRD data were collected on a high-resolution instrument, the pattern could not be indexed adequately on the previously described tetragonal unit cell. The structure of Li3Sb04 has therefore been reinvestigated, and we report the results here.
