The crystal chemistry of lithium in the alluaudite structure: A study of the (Na1-xLix)Cdln(2) (PO4)(3) the solid solution (x=0 to 1)

Several compounds of the (Na1-xLix)CdIn2(PO4)(3) solid solution were synthesized by a solid-state reaction in air, and pure alluaudite-like compounds were obtained for x = 0.00, 0.25, and 0.50. X-ray Rietveld refinements indicate the occurrence of Cd2+ in the M(1) site, and of In3+ in the M(2) site of the alluaudite structure. This non-disordered cationic distribution is confirmed by the sharpness of the infrared absorption bands. The distribution of Na+ and Li+ on the A(1) and A(2)' crystallographic sites cannot be accurately assessed by the Rietvled method, probably because the electronic densities involved in the Na+ --> Li+ substitution are very small. A comparison with the synthetic alluaudite-like compounds, (Na1-xLix)MnFe2(PO4)(3), indicates the influence of the cations occupying the M(1) and M(2) sites on the coordination polyhedra morphologies of the A(1) and A(2)' crystallographic sites. (C) 2002 Elsevier Science.