Rapid Solid-State Synthesis of Tantalum, Chromium, and Molybdenum Nitrides.

Solid-state metathesis (exchange) reactions can be used to synthesize many different transition-metal nitrides under ambient conditions including TiN, ZrN, and NbN. Typical metathesis reactions reach temperatures of greater than 1300 °C in a fraction of a second to produce these refractory materials in highly crystalline form. Likely due to the large amount of heat produced in these solid-state reactions, some transition-metal nitrides such as TaN, CrN, and γ-Mo2N cannot easily be synthesized under ambient conditions. Here metathesis reactions are demonstrated to produce the cubic nitrides TaN, CrN, and γ-Mo2N when sufficient pressure is applied before the reaction is initiated. By pressing a pellet of TaCl5 and Li3N with an embedded iron wire, crystalline cubic TaN forms under 45 kbar of pressure after a small current is used to initiate the chemical reaction. Crystalline cubic CrN is synthesized from CrCl3 and Li3N initiated under 49 kbar of pressure. Crystalline γ-Mo2N is produced from MoCl5 and Ca3N2 ...