Electrochemical Synthesis of Highly Nitrogen Containing γ‐ FeN 0.13 and ε ‐Fe 3 N 1.51 in a Molten Salt System

Two iron nitrides γ‐ FeN 0.13 and ε ‐Fe 3 N 1.51 were synthesized electrochemically in a molten salt system KCl–LiCl at 450 °C. For the electrochemical formation of γ‐ FeN 0.13 , which crystallizes in Fm 3 m with a = 367.46(7) pm, either Li 3 N or KNO 3 can be added to the salt mixture as nitrogen source. An addition of Li 3 N corresponds to anodic polarization (anodic electrolysis) of the working electrode and KNO 3 to cathodic polarization (cathodic electrolysis). The chosen applied voltages were 0.8 V and 1.4 V, respectively. Electrochemical synthesis employing a pure α‐iron foil as working electrode results in thicker layers than using an iron rod, independent of the polarization of the working electrodes. Cathodic electrolysis delivers a higher layer thickness compared to anodic electrolysis. Anodic electrolysis of a pure α‐iron foil at 2.2 V and a duration of 3 h provides ε ‐Fe 3 N 1.51 as bulk material. Structural refinements by the Rietveld method result in a hexagonal unit cell with parameters of a = 478.06(3) pm and c = 441.82(3) pm indicating the high nitrogen content in agreement with an elemental analysis.