Mechanistically Guided Materials Chemistry: Synthesis of Ternary Nitrides, CaZrN2 and CaHfN2

• DOI: 10.1021/jacs.3c12114
• Publication Date: 2024-01-31T06:42:30Z
• Authors: Christopher L. Rom; Andrew Novick; Matthew J. McDermott; Andrey A. Yakovenko; Jessica R. Gallawa; Gia Thinh Tran; Dominic C. Asebiah; Emily N. Storck; Brennan C. McBride; Rebecca C. Miller; Amy L. Prieto; Kristin A. Persson; Eric Toberer; Vladan Stevanović; Andriy Zakutayev; James R. Neilson
• Keywords: Condensed Matter - Materials Science; Materials Science (cond-mat.mtrl-sci); FOS: Physical sciences

Recent computational studies have predicted many new ternary nitrides, revealing synthetic opportunities in this underexplored phase space. However, synthesizing nitrides is difficult, part because intermediate and product phases often high cohesive energies that inhibit diffusion. Here, we report the synthesis of two phases, calcium zirconium nitride (CaZrN2) hafnium (CaHfN2), by solid state metathesis reactions between Ca3N2 MCl4 (M = Zr, Hf). Although reaction nominally proceeds to target a 1:1 ratio precursors via + → CaMN2 2 CaCl2, prepared way result Ca-poor materials (CaxM2–xN2, x < 1). A small excess (ca. 20 mol %) needed yield stoichiometric CaMN2, as confirmed high-resolution synchrotron powder X-ray diffraction. In situ diffraction reveal produce Zr3+ intermediates early pathway, reoxidize back Zr4+ oxidation CaZrN2. Analysis computationally derived chemical potential diagrams rationalizes approach its contrast from MgZrN2. These findings additionally highlight utility thermochemistry provide mechanistic guidance for synthesis.