  Ternary nitrides are of growing technological importance, with applications
as semiconductors, catalysts, and magnetic materials; however, new synthetic
tools are needed to advance materials discovery efforts. Here, we show that
Zn$_3$WN$_4$ can be synthesized via metathesis reactions between Li$_6$WN$_4$
and Zn$X_2$ ($X$ = Br, Cl, F). In situ synchrotron powder X-ray diffraction and
differential scanning calorimetry show that the reaction onset is correlated
with the Zn$X_2$ melting point and that product purity is inversely correlated
with the reaction's exothermicity. High resolution synchrotron powder X-ray
diffraction measurements show that this bulk synthesis produces a structure
with substantial cation ordering, as opposed to the disordered structure
initially discovered via thin film sputtering. Diffuse reflectance spectroscopy
reveals that Zn$_3$WN$_4$ powders exhibit two optical absorption onsets at 2.5
eV and 4.0 eV, indicating wide-bandgap semiconducting behavior and suggesting a
small amount of structural disorder. We hypothesize that this synthesis
strategy is generalizable because many potential Li-$M$-N precursors (where $M$
is a metal) are available for synthesizing new ternary nitride materials. This
work introduces a promising synthesis strategy that will accelerate the
discovery of novel functional ternary nitrides and other currently inaccessible
materials.
