Dalian University of Technology, China
Title: Different magnetic behaviors of Mg and Zn doped Fe3O4 nanoparticles estimated in terms of crystal domain size, universal dielectric response and application to anodes for lithium ion batteries
Masaru Matsuo has completed his PhD at Kyoto University in Japan and he was a professor of Nara Women’s University. After his retirement, he becomes a professor of Dalian University of Technology in China. He has published about 200 papers in refereed journal articles. He is one of IUPAC fellows and he received Paul Flory Polymer Research Prize on April 2009.
Magnesium (Mg) doped Fe3O4 nanoparticles representing as MgxFe3-xO4 ( ) was analyzed in comparison with zinc (Zn) doped Fe3O4, ZnxFe3-xO4. Magnetization vs. applied magnetic field for MgxFe3-xO4 particles provided the maximum saturation magnetization (Ms) with 69.4 emu/g at x=0.1 as super-paramagnetism, while the M5 by Zn-doping was 80.9 emu/g at x=0.2. The crystal unit volume (Vc) by Mg-doping at were constant but the crystal size decreased with increasing x. Further doping beyond x=0.6 provided small amorphous power aggregates which offer universal dielectric response implying highly disordered system. In contrast, the Vc 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 ZnxFe3-xO4 ( ) and MgxFe3-xO4 ( ) formed by a crystal domain were analyzed by a three-circuit model with one normal parallel circuit and two circuits with resistance and constant phase element (CPE). The stability of capacity as anode of lithium ion batteries was investigated for the composites prepared by adhering Mg2+, Fe2+and Fe3+ on sidewalls of as-modified multiwall carbon nanotubes (MWCNT), in which poly(vinylalcohol) (PVA) was used as a hydrogen bond functionalizing agent to modify MWCNTs. Among the ferrite composites, Zn0.2Fe2.8O4 provided the highest capacity with good stability under discharge and charge cycles. The reason is due to the highest crystal unit volume of Zn0.2Fe2.8O4 to accept lithium ions.