National Natural Science Foundation of China [40472027]; Natural Science and Engineering Research Council of CanadaA novel apatite-type compound, (Na2.5Bi2.5)(PO4)(3)(F,OH), NBPF, in the form of single-crystal microtubes with well-faceted, hexagonal morphologies in both exterior and interior surfaces, has been synthesized under hydrothermal conditions without addition of any template, surfactant or metal catalyst. Single crystal X-ray diffraction analysis confirms that Na+ and Bi3+ ions completely replace the Ca2+ ions in the apatite-like structure and jointly occupy three crystallographic sites with significantly different site preferences [Bi0.61Na0.39 at the 6c site, and Bi0.45Na0.55 and Bi0.23Na0.77 at the 2b sites, space group P6(3) (No. 173)]. Time-dependent experiments show that these NBPF microtubes form via a fluoride-induced, in situ chemical reaction nucleation-dissolution-recrystallization growth mechanism
