Modulation Of Optical And Magnetic Properties In Ta-Based Semiconductors By Doping

Photocatalytic hydrogen production from water splitting is of great significance in clean renewable energy. Semiconductor photocatalysts act as an important carrier of chemical energy conversion from solar energy, attracted wide attention. The tantalum-based semiconductor was widely used in many fields, especially in spintronics and photocatalysis, due to their distinctive electronic structure and chemical durability. Since the bandgap of tantalum-based semiconductors is between 3.8 eV and 4.0 eV, they are actived in the ultraviolet range. This restricts them to be used in the actual applications. Doping ions is an effective way to broaden the light absorption range of wide bandgap semiconductors. In the present work, we mainly focused on the bandgap modulation of Ta-based semiconductor. The results are as follows:?1? TaN was chosen as the precursor to synthesis self-doped N-Ta₂O₅ by hydrothermal method. The bandgap of Ta₂O₅ decreases from 4.0 eV to 2.2 eV when N atom replaces the O atom. A strong absorption can be obtained in the visible light for this system, which is identified by the photodegradation of methylene blue ?MB?. The photodegradation ratio of the samples can be achieved to about 80%.?2? Ta₂O₅ and alkaline aqueous NaOH were chosen as the reaction sources to synthesize Fe-doped NaTaO₃ ?FNTO? by the hydrothermal method. The results show that NaTa1-xFexO3 exhibits an orthorhombic perovskite phase when Fe exists as a form of Fe3+. The absorption edge of NaTa1-xFexO3 shifts to longer wavelength with increasing x, indicating that NaTa1-xFexO3 has clear visible light absorption properties, and its bandgap can be reduced to 1.77 eV. Moreover, NaTa1-xFexO3 exhibits room-temperature ferromagnetism when Fe atoms are doped into NaTaO₃ crystal lattice. The ferromagnetic generation can be explained by the dual exchange and the exchange coupling actions. At the same time, oxygen vacancies caused by doping play an important role for the ferromagnetic coupling. Therefore, Fe doping can control simultaneously the optical and magnetic properties of NaTaO₃ semiconductor.?3? Mn or Co doped NaTaO₃ were synthesized by the above method. Similarly, doping also can modulate the optical and magnetic properties of NaTaO₃. doping Mn and Co make the absorption band edge of NaTaO₃ extend from the ultraviolet to the visible light range, and its bandgap energy reduced to 1.72 eV and 1.56 eV, respectively. However, Mn or Co-doped NaTaO₃ exhibit low-temperature ferromagnetism. The Ms gradually enhances with the increase of doping contents in NaTa1-xMnxO3 becaused of the existed Mn3O4 phase having a bigger high coercivity and remnant magnetization. On the contrary, the Ms decreases with the increase of doping contents in NaTa1-xCoxO3.In short, we prepared Ta-based semiconductor nanomaterials by hydrothermal method. Nonmetal self-doping N-Ta₂O₅ nanocatalyst has a relatively higher catalytic activity. Doping with transition elements ?Mn?Fe?Co? into NaTaO₃ nanocubes can regulate the optical and magnetic properties simultaneously. The engineering methods of bandgap is significant for the development and application of the future semiconductor photocatalysts and memory devices.