Syntheses crystal structures and comparisons of rare-earth oxyapatites Ca2RE8(SiO4)6O2 (RE = La Nd Sm Eu or Yb) and NaLa9(SiO4)6O2

摘要

Six different rare-earth oxyapatites, including Ca2 RE 8(SiO4)6O2 (RE = La, Nd, Sm, Eu, or Yb) and NaLa9(SiO4)6O2, were synthesized using solution-based processes followed by cold pressing and sinter­ing. The crystal structures of the synthesized oxyapatites were determined from powder X-ray diffraction (P-XRD) and their chemistries verified with electron probe microanalysis (EPMA). All the oxyapatites were isostructural within the hexa­gonal space group P63/m and showed similar unit-cell parameters. The isolated [SiO4]⁴⁻ tetra­hedra in each crystal are linked by the cations at the 4f and 6h sites occupied by RE ³⁺ and Ca²⁺ in Ca2 RE 8(SiO4)6O2 or La³⁺ and Na⁺ in NaLa₉(SiO₄)₆O₂. The lattice parameters, cell volumes, and densities of the synthesized oxyapatites fit well to the trendlines calculated from literature values.