title: Synthesis and characterization of Li11Nd18Fe4O(39-δ).
abstract: Li(11)Nd(18)Fe(4)O(39-δ) has been synthesized by the solid-state reaction of pellets, covered with powder of the same composition to avoid lithium loss, with a final reaction temperature of 950 °C. This phase has been reported previously to have various stoichiometries: Li(5)Nd(4)FeO(10), Li(8)Nd(18)Fe(5)O(39), and Li(1.746)Nd(4.494)FeO(9.493). The crystal structure of Li(11)Nd(18)Fe(4)O(39-δ) is closely related to that reported previously for two of the other three compositions but contains extra Li and differences in Li/Fe site occupancies. Fe is present in a mixture of 3+ and 4+ oxidation states, as confirmed by Mössbauer spectroscopy. The oxygen content of 39 - δ is variable, depending on the processing conditions. Samples slow-cooled in air from 800 °C are semiconducting, attributed to the presence of Fe(4+) ions, whereas samples quenched from 950 °C in N(2) are insulating.
authors: Department of Materials Science and Engineering, University of Sheffield , Mappin Street, Sheffield S1 3JD, UK.
authors: Yao-Chang
authors: YC
authors: Chen
authors: Nik
authors: N
authors: Reeves-McLaren
authors: Paul A
authors: PA
authors: Bingham
authors: Susan D
authors: SD
authors: Forder
authors: Anthony R
authors: AR
authors: West