Direct Growth of Highly Crystalline, Idiomorphic Fluorapatite Crystals on a Polymer Substrate

Well-developed, idiomorphic one-dimensional (1D) crystals of fluorapatite (FAp) were successfully grown for the first time on a poly(ethylene terephthalate) (PET) substrate at 150 °C by the cooling of the KNO 3 −LiNO 3 flux. The grown 1D FAp crystals were transparent-colorless, hexagonal prisms bounded by well-developed six-sided {101̅0} and flat {0001} end faces, and elongated in the ⟨0001⟩ directions. Their average size was relatively large, reaching about 5.2 × 0.5 μm. In addtion, the 1D FAp crystal was of very good crystallinity because no defects were observed in its lattice image by transmission electron microscopy. Furthermore, high-quality, idiomorphic 1D crystals of FAp were tried to be grown directly on a PET substrate by the flux method. The PET surface was completely covered with aggregated FAp crystals, which were flowerlike in shape (hemisphere) with FAp rods radiating from a central nucleus.