Synthesis and ionic conduction of lanthanum-neodymium doped strontium phosphosilicate apatite

Mustapha Hidouri

Gabes University, Tunisia

Posters & Accepted Abstracts: Chem Sci J

Abstract :

The characterization and ionic conductivity of phosphosilicate apatites obtained by a coupled substitution of the divalent cation by a trivalent lanthanide or a tetravalent actinide ion and the trivalent groupment PO₄ by a tetravalent SiO₄ groupment in the general formula Me(XO₄)₆Y₂ (Me: divalent cation; XO₄: anionic groupment and Y: monovalent anion). Strontium phosphosilicate apatite doped with lanthanum and neodymium and whose chemical formula Sr8La2-xNdx(PO₄)₄(SiO₄)₂F₂ with 0≤x≤2 were physicochemically investigated. The materials were prepared via conventional solid state reactions. The analysis and characterization of the synthesized powders were conducted by means of several techniques. The ionic conductivity Ï? of the samples was measured via a complex impedance spectroscopy. The results showed that the double substitution of lanthanum-neodymium in strontium phosphosilicate fluorapatite was effective and well crystallized single-phase apatites were successively obtained. The molar ratio was of about 1.67 verifying the stoichiometry character of the powders. The a and c lattice parameters obtained from a structural refinement by the Rietveld method were found in decrease if the Nd content (x) rose. The 31P NMR (MAS) exhibited a single peak and the FTIR spectroscopy revealed the characteristic bands of phosphosilicated fluorapatite. The neodymium-lanthanum substitution was total according to the small size differences of the two cations. The measured ionic conductivity Ï? of the samples was found to depend simultaneously on the Nd content and more intensively on the heating temperature, the maximum was 1.73x10^-6 S.cm^-1 obtained at 780°C for x=2.