The Crystal Chemistry of Lithium in the Alluaudite Structure: A Study of the (Na1−xLix)CdIn2(PO4)3 Solid Solution (x=0 to 1)

Abstract Several compounds of the (Na 1− x Li x )CdIn 2 (PO 4 ) 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 Cd 2+ in the M (1) site, and of In 3+ 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, (Na 1− x Li x )MnFe 2 (PO 4 ) 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.