Magnetic Behaviors of Mg- and Zn-Doped Fe3O4 Nanoparticles Estimated in Terms of Crystal Domain Size, Dielectric Response, and Application of Fe3O4/Carbon Nanotube Composites to Anodes for Lithium Ion

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• 作者：Zhongyuan Lv ; Qi Wang ; Yuezhen Bin ; Ling Huang ; Rong Zhang ; Panpan Zhang ; Masaru Matsuo
• 刊名：Journal of Physical Chemistry C
• 出版年：2015
• 出版时间：November 19, 2015
• 年：2015
• 卷：119
• 期：46
• 页码：26128-26142
• 全文大小：1031K
• ISSN：1932-7455

文摘

Magnesium (Mg)-doped Fe₃O₄ nanoparticles represented as Mg_xFe_3鈥?i>xO₄ (0 < x 鈮?1) were analyzed in comparison with zinc (Zn)-doped Fe₃O₄, Zn_xFe_3鈥?i>xO₄. Magnetization versus applied magnetic field for Mg_xFe_3鈥?i>xO₄ particles provided the maximum saturation magnetization (M_s) with 69.37 emu/g at x = 0.1 as superparamagnetism, while the M_s by Zn-doping was 80.93 emu/g at x = 0.2. The crystal unit volume (V_c) by Mg doping at x 鈮?0.5 was constant, but the crystal size decreased with increasing x. Doping beyond x = 0.6 provided small amorphous power aggregates which offer universal dielectric response, implying a highly disordered system. In contrast, the V_c by Zn doping expanded up to x = 0.4 as the acceptable limit, which was attributed to the large difference between doping ion radius and replaced Fe³⁺ ion radius. On the other hand, the Mg_xFe_3鈥?i>xO₄ (0 鈮?x < 0.6) and Zn_xFe_3鈥?i>xO₄ (0 鈮?x 鈮?0.4) formed by a crystal domain were analyzed by a three-circuit model with one normal parallel circuit and two circuits with resistance and a constant-phase element (CPE). The stability of capacity as the anode of lithium ion batteries was investigated for the composites prepared by adhering Mg²⁺, Zn²⁺, and Fe³⁺ on the sidewalls of as-modified multiwall carbon nanotubes. Among the ferrite composites, Zn_0.2Fe_2.8O₄ provided the highest capacity with good stability under discharge and charge cycles.