Synthesis, structural model and vibrational spectroscopy of lutetium tricalcium phosphate Ca9Lu(PO4)7

Crystal Chemistry and Luminescence Properties of Eu-Doped Polycrystalline Hydroxyapatite Synthesized by Chemical Precipitation at Room Temperature

“…We note that the Ca2-O distances tend to decrease with increasing annealing temperature in the Eu-doped phase. In all the cases, all Ca-O distances are in good agreement with those observed in HAp [36,37] or generally in calcium phosphates [7,8,34]. The P-O distances within the P tetrahedron range from 1.495(7) Å to 1.587(12) Å (both in Eu-HAp450, Table 5) are in good agreement with similar P-O bond distances as found in powder X-ray structures from the Inorganic Crystal Structure Database [38].…”

The Rietveld Refinement in the EXPO Software: A Powerful Tool at the End of the Elaborate Crystal Structure Solution Pathway

“…The monitoring of the Rwp values of the Rietveld refinements confirmed the cation distributions proposed in [69] for RE = La, Pr, Nd, Eu, Gd, and Dy behavior due to steric reasons because of the large RE ionic radius. Three exceptions to the described trend are represented by RE = Tm, Yb [64] and Lu [65], entering in site M5 and not in M3 due to their lower ionic radius for 6-coordinations, allowing them to enter in the M5O6 compact octahedron. The refined site-occupancies provided a total charge very close to the ideal value of 21 valence units with minor anomalies (La and Nd the largest) within the experimental error provided by the EXPO software (see [64,65] for more details).…”

“…The automatic refinement executed by EXPO was robust and convergence ly achieved yielding Rwp = 2.787 and χ 2 = 1.846 (Table 1). Another example of Rietveld refinement concerns inorganic structures, in particular the study of a set of new rare-earth tricalcium phosphates (TCP) Ca 9 RE(PO 4 ) 7 (RE = La, Pr, Nd, Eu, Gd, Dy, Tm, Yb [64], and Lu [65]). TCP doped with rare earth (RE) elements are widely investigated because of their applications in biological imaging, owing to their strong luminescence properties [66,67].…”

Rietveld Refinement in the Characterization of Crystalline Materials

“…The automatic refinement executed by EXPO was robust and convergence was quickly achieved yielding R wp = 2.787 and χ 2 = 1.846 (Table 1). Another example of Rietveld refinement concerns inorganic structures, in particular the study of a set of new rare-earth tricalcium phosphates (TCP) Ca 9 RE(PO 4 ) 7 (RE = La, Pr, Nd, Eu, Gd, Dy, Tm, Yb [64], and Lu [65]). TCP doped with rare earth (RE) elements are widely investigated because of their applications in biological imaging, owing to their strong luminescence properties [66,67].…”

“…Atom labelling was fixed according to [71]. [65], entering in site M5 and not in M3 due to their lower ionic radius for 6-coordinations, allowing them to enter in the M5O 6 compact octahedron. The refined site-occupancies provided a total charge very close to the ideal value of 21 valence units with minor anomalies (La and Nd the largest) within the experimental error provided by the EXPO software (see [64,65] for more details).…”