Acta Crystallographica Section B

Structural Science

Volume 68, Part 5 (October 2012)


research papers



Acta Cryst. (2012). B68, 467-479    [ doi:10.1107/S0108768112019520 ]

Cl-OH ion-exchanging process in chlorapatite (Ca5(PO4)3Clx(OH)1 - x) - a deep insight

E. García-Tuñón, B. Dacuña, G. Zaragoza, J. Franco and F. Guitián

Abstract: We have synthesized large chlorapatite [ClAp, Ca5(PO4)3Clx(OH)1 - x, where x = 1] single crystals using the molten salt method. We have corroborated that the hexagonal symmetry P63/m describes the crystal structure best, even though the crystals are synthetic and stoichiometric. Moreover, we have performed several thermal treatments on these ClAp crystals, generating new single crystals in the apatite system [Ca5(PO4)3Clx(OH)1 - x, where x [less-than or equal to] 1], where the chloride anions (Cl-) were systematically substituted by hydroxyl anions (OH-). These new single crystals were methodically characterized by powder and single-crystal X-ray diffraction (SXRD), scanning electron microscopy (SEM), Fourier transform-IR spectroscopy (FT-IR), and energy-dispersive X-ray spectroscopy (EDS). We have discovered a previously unreported OH- inclusion site substituting the Cl- anion during the ion-exchanging process. Finally, we evaluated the atomic rearrangements of the other species involved in the structure. These movements are associated with ionic exchange, which can be justified from an energetic point of view. We also found a novel phase transformation at high temperature. When the crystals are heated over 1753 K the apatite system evolves to a less ordered monoclinic structure, in which the complete loss of the species in the anionic channel (Cl-, OH-) has been confirmed.

Keywords: chlorapatite (ClAp); ion exchanging; binary system; crystal phase transformations; structure changes.


fcfdisplay filedownload file

Structure factor file (CIF format) (20.5 kbytes)
[ doi:10.1107/S0108768112019520/zb5021h_room_needlesup2.fcf ]
Contains datablock h_room_needle


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Structure factor file (CIF format) (20.3 kbytes)
[ doi:10.1107/S0108768112019520/zb5021e_room_prismsup3.fcf ]
Contains datablock e_room_prism


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Structure factor file (CIF format) (20.5 kbytes)
[ doi:10.1107/S0108768112019520/zb5021c_room_prismsup4.fcf ]
Contains datablock c_room_prism


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Structure factor file (CIF format) (20.6 kbytes)
[ doi:10.1107/S0108768112019520/zb5021v_roomsup5.fcf ]
Contains datablock v_room


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Structure factor file (CIF format) (22.1 kbytes)
[ doi:10.1107/S0108768112019520/zb50211_low_needlesup6.fcf ]
Contains datablock a_low_needle


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Structure factor file (CIF format) (20.5 kbytes)
[ doi:10.1107/S0108768112019520/zb50212_low_prismsup7.fcf ]
Contains datablock d_low_prism


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Structure factor file (CIF format) (20.5 kbytes)
[ doi:10.1107/S0108768112019520/zb50213_low_prismsup8.fcf ]
Contains datablock f_low_prism


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Structure factor file (CIF format) (20.4 kbytes)
[ doi:10.1107/S0108768112019520/zb50214_low_needlesup9.fcf ]
Contains datablock b_low_needle


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Structure factor file (CIF format) (109.1 kbytes)
[ doi:10.1107/S0108768112019520/zb5021C_monosup10.fcf ]
Contains datablock C_mono


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Structure factor file (CIF format) (109.1 kbytes)
[ doi:10.1107/S0108768112019520/zb5021E_monosup11.fcf ]
Contains datablock E_mono


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Structure factor file (CIF format) (108.5 kbytes)
[ doi:10.1107/S0108768112019520/zb5021H_monosup12.fcf ]
Contains datablock H_mono


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Structure factor file (CIF format) (205.7 kbytes)
[ doi:10.1107/S0108768112019520/zb5021G_monosup13.fcf ]
Contains datablock G_mono


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Structure factor file (CIF format) (106.1 kbytes)
[ doi:10.1107/S0108768112019520/zb5021B_monosup14.fcf ]
Contains datablock B_mono


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Structure factor file (CIF format) (109.0 kbytes)
[ doi:10.1107/S0108768112019520/zb5021D_monosup15.fcf ]
Contains datablock D_mono


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Structure factor file (CIF format) (108.8 kbytes)
[ doi:10.1107/S0108768112019520/zb5021F_monosup16.fcf ]
Contains datablock F_mono


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Structure factor file (CIF format) (108.8 kbytes)
[ doi:10.1107/S0108768112019520/zb5021A_monosup17.fcf ]
Contains datablock A_mono


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Structure factor file (CIF format) (24.5 kbytes)
[ doi:10.1107/S0108768112019520/zb50211400lsup18.fcf ]
Contains datablock 1400l


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Structure factor file (CIF format) (20.5 kbytes)
[ doi:10.1107/S0108768112019520/zb50211400rsup19.fcf ]
Contains datablock 1400r


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Structure factor file (CIF format) (29.6 kbytes)
[ doi:10.1107/S0108768112019520/zb50211450lsup20.fcf ]
Contains datablock 1450l


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Structure factor file (CIF format) (20.2 kbytes)
[ doi:10.1107/S0108768112019520/zb50211450rsup21.fcf ]
Contains datablock 1450r


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Structure factor file (CIF format) (29.6 kbytes)
[ doi:10.1107/S0108768112019520/zb50211475lsup22.fcf ]
Contains datablock 1475l


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Structure factor file (CIF format) (20.0 kbytes)
[ doi:10.1107/S0108768112019520/zb50211475rsup23.fcf ]
Contains datablock 1475r


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Structure factor file (CIF format) (29.5 kbytes)
[ doi:10.1107/S0108768112019520/zb50211480lsup24.fcf ]
Contains datablock 1480l


fcfdisplay filedownload file

Structure factor file (CIF format) (19.8 kbytes)
[ doi:10.1107/S0108768112019520/zb50211480rsup25.fcf ]
Contains datablock 1480r


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Structure factor file (CIF format) (143.1 kbytes)
[ doi:10.1107/S0108768112019520/zb50211500lsup26.fcf ]
Contains datablock 1500l


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