Fe2 Si5 N8 : Access to Open-Shell Transition-Metal Nitridosilicates

Abstract

Highly condensed nitridosilicates doped with Eu²⁺ or Ce³⁺ play an important role in saving energy by converting the blue light of (In,Ga)N-LEDs. Although nitridosilicates are known for great structural variety based on covalent anionic Si-N networks, elemental variety is restricted. Presenting a significant extension of the latter, this work describes a general access to open-shell transition-metal nitridosilicates. As a proof-of-principle, the first iron nitridosilicate, namely Fe₂ Si₅ N₈ , was prepared by exchanging Ca²⁺ in α-Ca₂ Si₅ N₈ applying a FeCl₂ melt (salt metathesis). The title compound was analyzed by powder X-ray diffraction, EDX, ICP-OES, combustion analysis, TG/DSC, Mössbauer spectroscopy and magnetic susceptibility measurements. Furthermore, the structure of α-Ca₂ Si₅ N₈ was determined at 1073 and 1173 K confirming the anionic network of α-Ca₂ Si₅ N₈ providing possible migration pathways for the ion-exchange reaction.

Keywords: Mössbauer spectroscopy; ion exchange; iron; nitridosilicates; transition metals.