Elaboration, Rietveld refinements and vibrational spectroscopic study of Na1-xKxCaPb3(PO4)3 lacunar apatites (0⩽x⩽1) (original) (raw)
2015, Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy
Synthesis of apatites, Na1-xKxCaPb3(PO4)3 0⩽x⩽1, with anion vacancy were carried out using solid state reactions. The solid solution of apatite-type structure crystallize in the hexagonal system, space group P63/m (No. 176). Rietveld refinements showed that around 90% of Pb(2+) cations are located in the (6h) sites, the left amount of Pb(2+) cations are located in the (4f) sites; 27-31% of Ca(2+) cations are located in the (6h) sites, the left amount of Ca(2+) cations are located in the (4f) sites. The ninefold coordination sites (4f) are also occupied by the K(+) and Na(+) monovalent ions. The structure can be described as built up from [PO4](3-) tetrahedra and Pb(2+)/Ca(2+) of sixfold coordination cavities (6h positions), which delimit void hexagonal tunnels running along [001]. These tunnels are connected by cations of mixed sites (4f) which are half occupied by Pb(2+)/Ca(2+) and half by Na(+)/K(+) mixed cations. The assignment of the observed frequencies in the Raman and infrare...
Loading Preview
Sorry, preview is currently unavailable. You can download the paper by clicking the button above.