The Ternary Nitrides GaFe₃N and AlFe₃N: Improved Synthesis and Magnetic Properties

Abstract

The recently published two-step ammonolysis was adapted to the first synthesis of GaFe 3 N as a pure phase and AlFe 3 N with a very high phase purity. Similar to archetypal γ 0 -Fe 4 N (a = 3.7900(6) A ˚), the ternary nitride GaFe 3 N adopts a perovskite-like structure in space group Pm3m with a slightly enlarged lattice parameter of a = 3.7974(1) A ˚. The magnetic characterization clearly evidences that GaFe 3 N is an antiferromagnet. The systematic exchange of Ga by Fe in going from GaFe 3 N to γ 0 -Fe 4 N results in a change from antiferromagnetic to ferromagnetic behavior. In contrast, the homologous ternary nitride AlFe 3 N shows a statistical Al/Fe substitution which results in space group Fm3m. AlFe 3 N can be classified as a soft ferromagnetic nitride.

Antiperovskites with Exceptional Functionalities

“…In the case of iron‐containing antiperovskite nitrides, avoiding the formation of stable binary impurities is always difficult due to their lower formation energies. In this situation, a two‐step ammonolysis method combining a high‐temperature (1000–1300 °C) sintering step and a low‐temperature (500–600 °C) nitriding reaction was proposed to produce Fe 3 BN (B = Rh, Ga, Al) with improved phase purity . NH 3 was used as the ammonolysis agent.…”

Metal‐Rich Ternary Perovskite Nitrides

“…[127] Increasing substitution with Ga in cubic Fe 4-x Ga x N leads to a gradual transformation from ferro-to antiferromagnetic order upon approaching the limit of x slightly below unity. [128,129] Fe 4-x In x N exists fully ordered up to at least x = 0.8 as a cubic ferromagnet. [130] However, a sample obtained via mechanical alloying was found to show some Fe/In disorder and an indium content of up to x = 1.…”

“…[113] In strong contrast Fe 3 AlN was reported several times, but recently questioned, since obtained samples were shown to rather consist of an intimate mixture of γ′-Fe 4 N and amorphous aluminium oxide. [114,129,131]…”

Ammonia Decomposition and Synthesis over Multinary Magnesioferrites: Promotional Effect of Ga on Fe Catalysts for the Decomposition Reaction

“…According to temperature-dependent XRD measurements, the decomposition of GaFe 3 Nt akes place in this temperature window. [23] In situ XRD experiments carriedo ut over af reshly reduced MgFeGaO 4 sample suggests that this nitride phase is formed during catalysis. …”

“…Results from the in situ XRD measurements carriedo ut over MgFeGaO 4 are presented in Figure 8b.A ccording to the pattern obtained after reduction,t he phase composition is clearly more complex in comparison to the binary andt he Al-containing ferrite systems:w hereas ah igh amount of Fe/Ga-spinel [28] evolves, magnesiowüstite is only present to am uch smaller extent.T he quantity of both speciesi sn early constantd uring the entire catalytic run. The third phase can be identified as ab cc structure similar to a-Fe, which is knownt of orm as olid solution with Ga. [29] At 500 8C, the Ga-Fe solids olution undergoes at ransformation into (Fe,Ga)Fe 3 N, which adopts ap erovskite-likes tructure in space group Pm3 m. [23] As the temperature furtheri ncreases, (Fe,Ga)Fe 3 Ni sr educed to Fe 3 Ga that is isotypet oA uricupride (Pm3 m). [30] Precisely in this temperature regime N 2 evolution was observed during the NH 3 -TPD prior and after the temperature programmed NH 3 decomposition over MgFeGaO 4 ( Figure 7).…”