Minfeng Lu

Hole doping double perovskites Sr2FeMo1−xO6 (x = 0, 0.03, 0.04, 0.06) and their Mössbauer, crystal structure and magnetic properties

Crystal structure and magnetization behavior of double perovskite compounds Sr2FeMo1−xO6 (x = 0, 0.03, 0.04, 0.06) have been investigated using x-ray diffraction, Mossbauer spectroscopy and magnetization measurements. The proportion of Fe/Mo and the concentration of Mo vacancies determined by Rietveld methods and Mossbauer spectroscopy influence both the magnetic and magnetoresistive properties. An important fraction of the injected holes is localized at Mo sites, which is helpful for applications, because it promotes the occurrence of ordering between Fe and Mo cations. Both magnetic and Mossbauer spectroscopy data indicate that Mo hole doping strengthens the ferromagnetic interactions; moreover, 57Fe Mossbauer spectroscopy revealed that the iron with one Mo vacancy existed inside regions of iron ions with one or two irons as first cation neighbors. A dramatic enhancement of the ferromagnetic order is due to the increased energy difference between the Fe and Mo sites.

Effect of milling atmosphere on the hydriding properties of a Mg–amorphous Zr0.9Ti0.1(Ni0.57Mn0.28V0.1Co0.05)2.1 composite

The effect of milling atmosphere on the hydriding properties of a Mg-amorphous Zr0.9Ti0.1(Ni0.57Mn0.28V0.1Co0.05)(2.1) composite milled with a Spex8000 vibration mill was investigated by X-ray powder diffraction, SEM and TEM. The results indicated that, compared with the composite milled under Ar, the composite milled under H-2 showed superior hydriding performance. The brittle MgH2, which formed directly during the milling process under H-2 with the help of the amorphous phase Zr0.9Ti0.1(Ni0.57Mn0.28V0.1Co0.05)(2.1) and the mechanical driving force, resulted in a highly dispersive distribution of the amorphous phase in the Mg matrix and a smaller particle/grain size during the RMA process, which led to a remarkable decrease in the activation energy for hydrogen absorption

Hydrogen sites occupation in alpha-LaNi4Al hydride

The hydrogen sites occupation in La2Ni8Al2H has been investigated by a first-principle calculation to study the effect of the Al atom on the location of hydrogen and to explore the dominating factors to determine the hydrogen sites. It is found that the hydrogen cannot be stationed at interstitial sites surrounded by atoms including Al. Judged from the solution energy of hydrogen, the 12n site is most stable and the 4h site cannot accommodate H. The hydrogen occupation in LaNi4Al shows a distinct way from that in LaNi5, where five nonequivalent interstices (3f, 4h, 6m, 12o, 12n) have been reported to be available for the hydrogen in LaNi5. This indicates that the Al atom has important influence on the hydrogen occupation. The seems to be a parameter to measure the stability of La2Ni8Al2H. By analyzing the density of states combined with the local environment of sites, the bond order (BO) and average Mulliken charge (AMC), we found that the 12n and 3f sites have similar atomic and electronic structure and the covalence and ionicity. The 3f site is also favorite occupation for hydrogen besides the 12n site.