Navigating the thermodynamic landscape in search of synthetic routes to ternary nitrides

Abstract

Ternary nitride materials—a class of ceramics composed of two different metals bound with anionic nitrogen (N3-) as a solid—are underexplored because they are difficult to make. Nitrides rarely occur in nature, as the oxygen in the air (O2) is more reactive towards metals than the nitrogen (N2). Consequently, oxide minerals dominate the earth's crust while nitride minerals are extremely rare. Almost all ternary nitrides that have been discovered have synthesized, usually with rigorously air-free conditions. Despite much effort in the past century, the number of known ternary nitrides (approximately 450) pales in comparison to that of ternary oxides (over 4,000). Yet there are world-changing materials within this small number of compounds, like the (In,Ga)N alloys that underpin efficient blue light emitting diodes. Fortunately, recent computational work has predicted a number of theoretically stable ternary nitrides, providing targets for synthesis. This dissertation focuses on the synthesis of new ternary nitrides. Guided by increasingly user-friendly computational tools, these chapters describe syntheses overcome the thermodynamic barriers that often inhibit the formation of new ternary nitrides. Along the way, several new materials are discovered and characterized for promising magnetic and semiconducting properties: MnSnN2, MgWN2 in two structure types, Mg3WN4, MgZrN2, CaZrN2, and CaHfN2. These adventures in synthesis not only report new compounds, but also highlight promising strategies for future explorations of uncharted nitride phase space.