Elaboration, Rietveld refinements and vibrational spectroscopic study of Na1-xKxCaPb3(PO4)3 lacunar apatites (0 < x < 1)
2015 (English)In: Spectrochimica Acta Part A - Molecular and Biomolecular Spectroscopy, ISSN 1386-1425, E-ISSN 1873-3557, Vol. 145, 493-499 p.Article in journal (Refereed) Published
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 P6(3)/m (No. 176). Rietveld refinements showed that around 90% of Pb2+ cations are located in the (6h) sites, the left amount of Pb2+ cations are located in the (4f) sites; 27-31% of Ca2+ cations are located in the (6h) sites, the left amount of Ca2+ 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 Pb2+/Ca2+ of sixfold coordination cavities (6h positions), which delimit void hexagonal tunnels running along . These tunnels are connected by cations of mixed sites (4f) which are half occupied by Pb2+/Ca2+ and half by Na+/K+ mixed cations. The assignment of the observed frequencies in the Raman and infrared spectra is discussed on the basis of a unit cell group analysis and by comparison with other apatites. Vibrational spectra of all the compositions are similar and show some linear shifts of the frequencies as a function of the composition toward lower values due the substitutions of Na+ by K+ with a larger radius.
Place, publisher, year, edition, pages
2015. Vol. 145, 493-499 p.
Research subject Earth Science with specialization in Mineral Chemistry, Petrology and Tectonics
IdentifiersURN: urn:nbn:se:uu:diva-241001DOI: 10.1016/j.saa.2015.02.083ISI: 000353754700060PubMedID: 25797224OAI: oai:DiVA.org:uu-241001DiVA: diva2:777389