Abstract
Britholites are considered as potential matrices for storage of nuclear wastes such as minor actinides and long-lived fission byproducts. This investigation is concerned with the study of simultaneous substitution in calcium fluor-britholite framework of two lanthanide ions assimilated to radionuclides. A series of calcium fluorbritholites doped with lanthanum and neodymium Ca8La2-xNdx(PO4)4(SiO4)2F2 with 0 ≤ x ≤ 2 were prepared via a solid state reaction in the temperature range 1450℃- 1250℃. The obtained products were characterized by several techniques such as Chemical analysis via Inductively coupled plasma Atomic emission spectrometry ICP-AES, X-ray diffraction (XRD), Fourier transformed infrared spectroscopy FTIR and Nuclear magnetic resonance 31P NMR (MAS). Obtained solid solutions containing lanthanum and neodymium in variable proportions were typically apatite of hexagonal structure P63/m spatial group. The stoichiometry of the powders was verified via the metal/(phosphate + silicate) molar ratios found at about 1.67. The lattice parameters a and c calculated by the Rietveld method decreased as neodymium level increased. Despite, the close respective sizes of lanthanum and neodymium ions (VIrLa3+= 1.032A, VIrNd3+= 0.983A), their mutual substitutions led to solid solutions in whole range of composition with preferential occupation of Me (2) sites.
Highlights
Britholites are considered as potential matrices for storage of nuclear wastes such as minor actinides and long-lived fission byproducts. This investigation is concerned with the study of simultaneous substitution in calcium fluor-britholite framework of two lanthanide ions assimilated to radionuclides
Their indexation was made with reference to the Ca10(PO4)6F2 phase (JCPDS card 01-076-0558), shows that the different synthesized samples are characteristic of a single-phase apatite with hexagonal symmetry spatial group P63/m
[33], the solid solution doped with lanthanum and neodymium was formed and the substitution was in whole range
Summary
Calcium phosphate apatites are frequently used in orthopedic and dentistry surgery as a substitute for failing bones and teeth [15] [16] [17] [18] These compounds have shown interesting properties of bioactivity and osteoconduction as well as a chemical composition and a crystal structure similar to that of the mineral part of calcified tissue [19] [20] [21]. New applications in the field of the environment have appeared; apatitic derivatives with coupled substitutions of divalent cations by rare earth elements (lanthanides: Ln3+ or actinides: Ac3+) and the silicates SiO44− partially substitute XO4 groups Such a family, called britholites, acted as a matrix for conditioning certain radionuclides and heavy metals [23] [24] [25]. All specimens will be afterwards abbreviated according to the index that bears the La3+ and Nd3+ ions as CaLa2F, CaLa1.5Nd0.5F, CaLa1Nd1F, CaLa0.5Nd1.5F and CaNd2F
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