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Multiferroic pure and Er-doped BiFeO3 thin films were prepared using a sol–gel technique. The effect of Er-doped concentration on the crystal structure and on the ferroelectric and leakage current properties of BiFeO3 films were studied in detail. The study showed the enhanced ferroelectric polarization and reduced leakage current density that occurred after doping Er. Such improved ferroelectric and leakage properties are attributed to ferroelectric distortion and to the change of leakage current conduction mechanisms derived from the structural transformation that occurred after doping Er. The rhombohedral structure of pure BiFeO3 transforms to the coexistence of tetragonal and orthorhombic symmetry structure as Er-doped concentration x increased gradually to 0.15, then to the orthorhombic structure when x = 0.20. The present work provides an easy method to decrease the leakage current and improve the ferroelectric properties of BiFeO3 films.

Au nanoparticles (AuNPs) are successfully assembled on TiO2 nanotube (TN) arrays through electrochemical deposition technology to improve the surface characteristics of TN arrays as an implant material. The loading amount of AuNPs can be controlled by adjusting the deposition time of electrochemical deposition. The effect of the amount of the loaded AuNPs on surface roughness and surface energy is systematically investigated on the basis of various characterizations. Results show that the increase in the loading amount of AuNPs on the TN arrays can increase surface roughness and decrease surface energy. Potentiodynamic polarization tests indicate that AuNP-modified TNs possess a higher corrosion resistance than unmodified TNs. Corrosion resistance increases as the amount of the loaded AuNP increases. In vitro cell culture tests are performed on the basis of cell morphology observations and MTT assays. Osteoblast cell adhesion and proliferation ability on the AuNP-modified TN surface are greater than those on the unmodified TN surface. The sample fabricated at the deposition time of 90 s exhibits an optimum cell performance. This work can provide a new platform to develop the surface chemistry of TN arrays and to fabricate titanium-based implant materials to enhance bioactivity.

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