Synthesis, structure refinement and vibrational spectroscopy of new rare-earth tricalcium phosphates Ca9RE(PO4)7 (RE = La, Pr, Nd, Eu, Gd, Dy, Tm, Yb)

Rietveld Refinement in the Characterization of Crystalline Materials

“…[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).…”

“…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].…”

“…The monitoring of the R wp 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…”

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].…”