Comparison of synthetic and mineral fluorapatite, Ca5 (PO4)3F, in crystallographic detail

Sudarsanan, K.; Mackie, P. E.; Young, R. A.

doi:10.1016/0025-5408(72)90113-4

Cited by 180 publications

(107 citation statements)

References 7 publications

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“…As shown in Figure 3a and Table 3, and using the FAp of Sudarsanan et al (1972) and the Gd-rich FAp of Fleet & Pan (1995) as reference compounds, the Ca1-O bond distances and (Ca1)O 9 polyhedron volume of AP30-1 and AP40-0 are consistent with the Gd siteoccupancy data in Ca1, as obtained from the type-1 refinement. However, the bond distances and volumes for the (Ca2)O 6 X polyhedron are not informative in this respect (Fig.…”

Section: Comparison Of Site-occupancy Ratios From W-band Epr and X-rasupporting

confidence: 68%

“…The site-occupancy ratio from the type-1 refinement, in which the Gd content of the Ca2 position was refined, [0.8 (2)] is the preferred value because this refinement procedure was adopted in all of our previous structural studies on REEsubstituted apatite-group minerals (Fleet & Pan 1995, 1997a, Fleet et al 2000a. The progressive change in size of the (Ca1)O 9 polyhedron with increasing Gd content from FAp (Sudarsanan et al 1972) to AP30-1, AP40-0, and the Gd-rich FAp of Fleet & Pan (1995) supports the presently accepted site-occupancy ratio for Gd in AP30-1. The spatial accommodation of REE 3+ cations and anions X (F -, OH -and Cl -) in the apatite structure was discussed in Fleet et al (2000a, b).…”

Section: Comparison Of Site-occupancy Ratios From W-band Epr and X-rasupporting

confidence: 58%

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SITE PREFERENCE OF Gd IN SYNTHETIC FLUORAPATITE BY SINGLE-CRYSTAL W-BAND EPR AND X-RAY REFINEMENT OF THE STRUCTURE: A COMPARATIVE STUDY

Pan¹,

Fleet²,

Chen³

et al. 2002

The Canadian Mineralogist

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Fluorapatite containing 1.2(2) wt% Gd 2 O 3 (sample AP30-1), synthesized from a CaF 2 -rich melt in a Pt crucible, has been investigated by single-crystal W-band (~94 GHz) electron paramagnetic resonance (EPR) spectroscopy and X-ray structure refinement. The EPR spectrum of AP30-1 measured at ~287 K, with Zeeman field B // z' and microwave field B // x', gave a Gd site-occupancy ratio ( Ca2 Gd/ Ca1 Gd) of 1.4(4), indicating a weak preference between the two types of Ca sites. Similarly, X-ray refinement of the structure of AP30-1 suggests that Gd is essentially equally distributed between the two Ca sites: Ca2Gd/ Ca1 Gd = 0.8(2), although the Gd content in this sample is close to the practical limit of detection of this method. This agreement between the W-band EPR and X-ray structural data confirms that EPR is capable of determining the distribution of paramagnetic trace elements between structurally nonequivalent positions in minerals. X-ray refinement of the structure of another sample of fluorapatite [AP40-0, containing 2.9(1) wt% Gd 2 O 3 ] synthesized in a sealed Pt capsule, yielded a Ca2Gd/ Ca1 Gd value of 3.1(6), indicating a marked preference for the Ca2 site, consistent with the site preference of Gd in hydrothermally grown Gd-rich fluorapatite. The marked preference of Gd for the Ca1 site observed in previous EPR studies of flux-grown fluorapatite samples [AP30-0, 0.8(1) ppm Gd and Ca2 Gd/ Ca1 Gd = 0.13; AP30-5, 57(4) ppm Gd and Ca2 Gd/ Ca1 Gd = 0.20] is now attributed to the presence of Ca 2+ vacancies at ppm concentrations in these crystals. These point defects are unlikely to reach appreciable (weight %) concentrations in fluorapatite crystals synthesized from CaF 2 -rich melts, and hence the normal preference of Gd for the Ca2 site in AP30-1 and AP40-0.Keywords: gadolinium, fluorapatite, single-crystal W-band EPR, X-ray structure refinement, site preference, substitution mechanisms, point defects. SOMMAIRENous avons étudié un monocristal de fluorapatite contenant 1.2(2)% Gd 2 O 3 par poids (AP30-1), synthétisé à partir d'un bain fondu de CaF 2 dans un récipient en platine, au moyen de la résonance paramagnétique des électrons (RPE) dans la bande W (~94 GHz) et par affinement de la structure par diffraction X. Le spectre RPE de AP30-1, mesuré à ~287 K, avec un champ Zeeman B // z' et un champ micro-onde B // x', indique un rapport de l'occupation des sites Ca par le Gd ( une légère différence en préférence entre les deux sortes de sites Ca. De même, l'affinement de la structure de AP30-1 montre que le Gd serait réparti essentiellement également entre les deux sites: Ca2Gd/ Ca1 Gd = 0.8(2), quoique la teneur en Gd dans cet échantillon se rapproche de la limite de détection de cette méthode. Cette concordance entre la bande W du spectre RPE et les données sur la structure confirme que la spectroscopie RPE constitue un moyen révélateur pour déterminer la distribution des éléments traces paramagnétiques distribués sur des sites non-équivalents des minéraux. L'affinement de la structure d'un aut...

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Section: Comparison Of Site-occupancy Ratios From W-band Epr and X-rasupporting

confidence: 68%

Section: Comparison Of Site-occupancy Ratios From W-band Epr and X-rasupporting

confidence: 58%

SITE PREFERENCE OF Gd IN SYNTHETIC FLUORAPATITE BY SINGLE-CRYSTAL W-BAND EPR AND X-RAY REFINEMENT OF THE STRUCTURE: A COMPARATIVE STUDY

Pan¹,

Fleet²,

Chen³

et al. 2002

The Canadian Mineralogist

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“…Others disagree (e.g. Prince, 1981Prince, , 1985 and we point out the consistency between our results from duplicate data sets, between the duplicated data sets themselves (shown above) and the agreement of the 0%Sb positional parameters with those of Sudarsanan, Mackie & Young (1972). Furthermore, in no case of which we are aware has more than a factor of two misestimation been claimed for structural parameters.…”

Section: Precision Of the Rietveld Refinement Resultssupporting

confidence: 52%

“…The atomic positions and pattern parameters (peak widths, cell dimensions, true zero of 20, background function, preferred orientation parameter, etc.) were also varied, but the individual anisotropic thermal parameters were held fixed at the values found in a precise single-crystal determination (Sudarsanan, Mackie & Young, 1972) and only a single overall isotropic thermal motion parameter varied. These crystal structure refinements were carried out in space group P63/m using the Rietveld whole-pattern-fitting structure refinement method (Rietveld, 1969;Wiles & Young, 1981) by means of a recent version of computer program DBW3.2, which is an upgraded version of the program described by Wiles & Young (1981).…”

Section: Rietveld Refinements 2%sb Samplementioning

confidence: 99%

Determination of the antimony substitution site in calcium fluorapatite from powder X-ray diffraction data

DeBoer¹,

Sakthivel²,

Cagle³

et al. 1991

Acta Crystallogr Sect B

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Comparison of powder X-ray diffraction data from a 2-2 wt% antimony-substituted calcium fluorapatite [0.185 Sb atoms per unit cell containing CaloF2(PO4)6] with data from an undoped sample shows electron density changes corresponding to antimony substitution at the Ca(2) (mirror) site. Many properties of this 2.2 wt% Sb sample indicate that it corresponds to commercial halophosphate phosphors of lower Sb concentration. Differing properties are shown by a 3.1 wt% Sb sample for which no diffraction evidence is found for substitution at the Ca(2) site, but for which electron density difference maps do suggest substitution at the Wyckoff 2(c) and 2(d) sites of P63/m, between Ca(l) (threefold) positions. Both Rietveld refinements and Fourier inversion of the differences between observed intensities were used to reach these conclusions.

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“…The structure of apatite Ca 10 (PO 4 ) 6 A 2 A=F, OH, Cl apatite in the space group P6 3 /m allows a wide range of cation and anion substitutions [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16]. In fact, the two Ca positions have distinct stereochemistries (Ca(1), equipoint 4f, CaO 9 polyhedron, Ca(2), equipoint 6 h, CaO 6 (A polyhedron)) are able to accommodate a variety of univalent, divalent, and trivalent cations as substituents.…”

Section: Introductionmentioning

confidence: 99%

X-ray structure refinement, vibrational spectroscopy, and ionic conductivity of Na0.11Ca9.64Sm0.23(PO4)6F2

Boujelbene

Mhiri

2014

Ionics

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The present paper is interested in the study of compounds from the apatite family, which is an apatite structure of individual rare earth substituted fluorapatite. In fact, an Sm-Bearing fluorapatite Ca 10-2y Na y Sm y (PO 4 ) 6 A 2 with x=0.11 and y=0.23 has been synthesized by solidstate reaction and characterized by X-ray powder diffraction. The site occupancies of substituents are 0.01091 for Sm and 0.02601 for Na in the Ca(1) position and 0.05317 for Sm in the Ca(2) position. Besides, the observed frequencies in the Raman and infrared spectra were explained and discussed on the basis of unit cell group analyses and in comparison with fluorapatite and other fluorapatites. In addition to the proton conduction, the possibility of a Na + contribution to the conductivity in the high-temperature phase is proposed. The highest overall conductivity values were found at σ 475°C =2.03×10−5 S cm −1 and Ea=0.60 eV.

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Comparison of synthetic and mineral fluorapatite, Ca5 (PO4)3F, in crystallographic detail

Cited by 180 publications

References 7 publications

SITE PREFERENCE OF Gd IN SYNTHETIC FLUORAPATITE BY SINGLE-CRYSTAL W-BAND EPR AND X-RAY REFINEMENT OF THE STRUCTURE: A COMPARATIVE STUDY

SITE PREFERENCE OF Gd IN SYNTHETIC FLUORAPATITE BY SINGLE-CRYSTAL W-BAND EPR AND X-RAY REFINEMENT OF THE STRUCTURE: A COMPARATIVE STUDY

Determination of the antimony substitution site in calcium fluorapatite from powder X-ray diffraction data

X-ray structure refinement, vibrational spectroscopy, and ionic conductivity of Na0.11Ca9.64Sm0.23(PO4)6F2

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